UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

ALTAIR ENGINEERING INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

Dear Altair Engineering Inc. Stockholder:

On October 30, 2024, Altair Engineering Inc. (“Altair”), Siemens Industry Software Inc. (“Siemens Industry”) and Astra Merger Sub Inc., a wholly owned subsidiary of Siemens Industry (“Merger Sub”), entered into an Agreement and Plan of Merger that provides for the acquisition of Altair by Siemens Industry (such agreement, as it may be amended from time to time, the “merger agreement”). Pursuant to the terms of the merger agreement, Merger Sub will merge with and into Altair (the “merger”) with Altair surviving the merger as a wholly owned subsidiary of Siemens Industry (the “surviving corporation”). The respective boards of directors of Altair and Siemens Industry have unanimously approved the merger agreement and the merger. The accompanying proxy statement is dated December 18, 2024 and is first being mailed to Altair stockholders on or about December 18, 2024.

Upon the terms and subject to the conditions of the merger agreement, at the effective time of the merger, you will be entitled to receive, for each share of Class A Common Stock of Altair, par value $0.0001 per share (the “Class A common stock”) and each share of Class B Common Stock of Altair, par value $0.0001 per share (the “Class B common stock” and, together with the Class A common stock, the “Altair common stock”), that you own immediately prior to the effective time of the merger, $113.00 in cash without interest (the “merger consideration”), unless you have properly exercised your appraisal rights in accordance with Section 262 of the General Corporation Law of the State of Delaware (the “DGCL”), as more fully described in the accompanying proxy statement. The merger consideration represents an approximately 19% premium to the closing price of the Class A common stock on October 21, 2024, the last trading day prior to media speculation regarding a potential acquisition of Altair, an approximately 23% premium over the 6-month volume weighted average closing price of the Class A common stock for the period ending October 21, 2024, and an approximately 51% premium to the closing price of the Class A common stock on December 21, 2023, the last trading day prior to the leak regarding the acquisition of Ansys, Inc. (“Ansys”) by Synopsys, Inc. (“Synopsys”).

The Altair board of directors has unanimously (i) determined that the merger agreement and the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions set forth in the merger agreement, are fair to and in the best interests of Altair and its stockholders, (ii) declared the merger agreement and the transactions contemplated by the merger agreement, including the merger, advisable, (iii) approved the merger agreement, the execution and delivery by Altair of the merger agreement, the performance by Altair of the agreements contained in the merger agreement and the consummation of the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions contained in the merger agreement, (iv) directed that the adoption of the merger agreement be submitted to a vote at a meeting of Altair stockholders and (v) resolved to recommend adoption of the merger agreement and the transactions contemplated by the merger agreement, including the merger, to Altair stockholders.

At the special meeting of Altair stockholders described in the accompanying proxy statement (the “special meeting”), you will be asked to approve the merger agreement proposal and to vote on other merger-related matters. The Altair board of directors unanimously recommends that Altair stockholders vote (1) “FOR” the merger agreement proposal and (2) “FOR” each of the other proposals described in the accompanying proxy statement.

Your vote is very important regardless of the number of shares of Altair common stock that you own. Siemens Industry and Altair cannot complete the merger without the approval of the merger agreement proposal by Altair stockholders holding at least a majority of the voting power of the shares of Altair common stock

outstanding at the close of business on December 17, 2024, the record date for the special meeting. The failure of any Altair stockholder to vote will have the same effect as a vote “AGAINST” the approval of the merger agreement proposal. Whether or not you plan to participate in the special meeting, Altair urges you to submit a proxy in advance of the special meeting to have your shares voted by using one of the methods described in the accompanying proxy statement. If your shares are held in the name of a bank, brokerage firm or other nominee, please follow the instructions on the voting instruction card furnished by such bank, brokerage firm or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals to be considered at the special meeting without your instructions. If you do not provide your bank, broker or other nominee with any voting instructions, your shares of Altair common stock will not be counted for purposes of a quorum and will not be voted at the special meeting, which will have the same effect as a vote “AGAINST” the merger agreement proposal. As a result, you must provide voting instructions by filling out the voting instruction card in order for your shares to be voted. More information about Siemens Industry, Altair, the special meeting, the merger and the other proposals for consideration at the special meeting is contained in the accompanying proxy statement. Please carefully read the entire proxy statement and the annexes and documents included in, or incorporated by reference into, the proxy statement.

On behalf of the Altair board of directors, thank you for your continued support.

Sincerely,

/s/ James R. Scapa

James R. Scapa

Chairman of the Board and Chief Executive Officer

NEITHER THE U.S. SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED THE MERGER, PASSED UPON THE MERITS OF THE MERGER AGREEMENT, THE MERGER OR THE OTHER TRANSACTIONS CONTEMPLATED BY THE MERGER AGREEMENT OR DETERMINED IF THE ACCOMPANYING PROXY STATEMENT IS ACCURATE OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

Altair Engineering Inc.

1820 East Big Beaver Road

Troy, Michigan 48083

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON JANUARY 22, 2025

Dear Altair Engineering Inc. Stockholder:

This is a notice that the special meeting of stockholders of Altair Engineering Inc. (“Altair”) will be held on January 22, 2025, beginning at 10:00 a.m., Eastern Time (such meeting, including any adjournments or postponements thereof, the “special meeting”). The special meeting will be a completely virtual, live audio webcast meeting of stockholders and will be held for the following purposes:

The proxy statement of which this notice is a part (a) incorporates important business and financial information about Altair, Siemens Industry and Merger Sub from other documents that Altair has filed with the U.S. Securities and Exchange Commission (the “SEC”) and that are contained in or incorporated by reference into this proxy statement and (b) provides a detailed description of the merger and the merger agreement and the other matters to be considered at the special meeting, including the proposals listed above. Please refer to the accompanying proxy statement, including the merger agreement and the other annexes and documents included in, or incorporated by reference into, the accompanying proxy statement for further information with respect to the business to be transacted at the special meeting. You are encouraged to read the entire proxy statement carefully before voting. The Altair board of directors has unanimously (i) determined that the merger agreement and the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions set forth in the merger agreement, are fair to and in the best interests of Altair and its stockholders, (ii) declared the merger agreement and the transactions contemplated by the merger agreement, including the merger, advisable, (iii) approved the merger agreement, the execution and delivery by Altair of the merger agreement, the performance by Altair of the agreements contained in the merger agreement and the consummation of the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions contained in the merger agreement, (iv) directed that the adoption of the merger agreement be submitted to a vote at a meeting of Altair stockholders and (v) resolved to recommend adoption of the merger agreement and the transactions contemplated by the merger agreement, including the merger, to Altair stockholders.

The Altair board of directors unanimously recommends that Altair stockholders vote (1) “FOR” the merger agreement proposal, (2) “FOR” the merger-related compensation proposal and (3) “FOR” the adjournment proposal.

The Altair board of directors has fixed the close of business on December 17, 2024, as the record date for determination of Altair stockholders entitled to receive notice of, and to vote at, the special meeting or any adjournments or postponements thereof (the “record date”). Only holders of record of Class A Common Stock of Altair, par value $0.0001 per share (the “Class A common stock”) and Class B Common Stock of Altair, par value $0.0001 per share (the “Class B common stock” and, together with the Class A common stock, the “Altair common stock”) as of the close of business on the record date are entitled to receive notice of, and to vote at, the special meeting.

Under Delaware law, holders of Altair common stock who do not vote in favor of the merger agreement proposal will have the right to seek appraisal and obtain payment in cash for the fair value of their shares of Altair common stock, as determined by the Court of Chancery of the State of Delaware if the merger is completed, but only if they strictly comply with the procedures prescribed by Delaware law. These procedures are summarized in “Appraisal Rights of Altair Stockholders” beginning on page 113 of the accompanying proxy statement. In addition, the text of the applicable provisions of Delaware law is attached as Annex F to the accompanying proxy statement.

YOUR VOTE IS VERY IMPORTANT, REGARDLESS OF THE NUMBER OF SHARES THAT YOU OWN.

The merger cannot be completed unless the merger agreement proposal is approved by the affirmative vote, virtually or by proxy, of holders of at least a majority of the voting power of Altair common stock outstanding and entitled to vote thereon. The shares of Class A common stock and Class B common stock will be voted together as a single class on all matters submitted to stockholders at the special meeting, provided that each share of Class B common stock will be entitled to ten votes per share, while each share of Class A common stock will be entitled to one vote per share.

If you fail to (1) return your proxy card, (2) grant your proxy electronically over the internet or by telephone or (3) attend the special meeting in person (virtually), your shares will not be counted for purposes of determining whether a quorum is present at the special meeting. If a quorum is present and you fail to take one of the three foregoing steps, your shares will have the same effect as if they were voted “AGAINST” the proposal to adopt the merger agreement, but will have no effect on the other proposals.

Whether or not you expect to participate in the special meeting, Altair urges you to submit a proxy to have your shares voted “FOR” the proposal to adopt the merger agreement as promptly as possible either: (1) via the internet at www.proxyvote.com (see the enclosed proxy card for instructions); (2) by telephone (see the enclosed proxy card for instructions); or (3) by completing, signing and returning the enclosed proxy card in the postage-paid envelope provided, so that your shares may be represented and voted at the special meeting. If your shares are held in “street name” by a bank, brokerage firm or other nominee, please follow the instructions on the voting instruction card furnished by such bank, brokerage firm or other nominee. Any stockholder of record participating in the special meeting may vote even if such stockholder has returned a proxy card. However, if your shares are held in “street name” you must obtain a “legal proxy” from the bank, brokerage firm or other nominee to vote at the special meeting.

Altair stockholders of record as of December 17, 2024 will be able to participate in the special meeting by visiting www.virtualshareholdermeeting.com/ALTR2025SM and entering the 16-digit control number included on your proxy card or voting instruction card that accompanied your proxy materials. If you would like to view the special meeting materials via the internet, please visit www.proxydocs.com/ALTR.

If you have any questions about the special meeting, the merger, the proposals or the accompanying proxy statement, would like additional copies of this proxy statement, need to obtain proxy cards or other information related to this proxy solicitation or need help submitting a proxy or voting your shares of Altair common stock, you should contact:

Altair Engineering Inc.

Attention: Chief Legal Officer

1820 East Big Beaver Road

Troy, Michigan 48083

(248) 614-2400 x453

By order of the Altair board of directors,

/s/ Raoul Maitra

Raoul Maitra

Chief Legal Officer and Secretary

Dated: December 18, 2024

Troy, Michigan

Altair Engineering Inc.

1820 East Big Beaver Road, Troy, Michigan 48083

ALTAIR ENGINEERING INC.

PROXY STATEMENT

SPECIAL MEETING OF STOCKHOLDERS

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QUESTIONS AND ANSWERS

The following are some questions that you, as an Altair stockholder, may have regarding the merger and the special meeting and the answers to those questions. Altair urges you to carefully read the remainder of this proxy statement because the information in this section does not provide all the information that might be important to you with respect to the merger and the special meeting. Additional important information is also contained in the annexes to and the documents incorporated by reference into this proxy statement.

Q: What is the purpose of the special meeting?

A: At the special meeting, stockholders will consider and act upon the matters outlined in the notice of meeting on the cover page of this proxy statement, namely:

Q: Where and when is the special meeting?

A: The special meeting will be held on January 22, 2025, beginning at 10:00 a.m., Eastern Time (with log-in beginning at 9:45 a.m., Eastern Time), unless postponed to a later date. The special meeting will be a virtual only meeting conducted via live audio webcast at www.virtualshareholdermeeting.com/ALTAIR2025SM. You will need the 16-digit control number provided on your proxy card or voting instruction card in order to participate in the special meeting. Because the special meeting is completed virtually and being conducted via live webcast, stockholders will not be able to attend the meeting in person. If you would like to view the special meeting materials via the internet, please visit www.proxydocs.com/ALTR.

Q: How does the Altair board of directors recommend that I vote on the proposals?

A: The Altair board of directors unanimously recommends that Altair stockholders vote (1) “FOR” the merger agreement proposal, (2) “FOR” the merger-related compensation amendment proposal and (3) “FOR” the adjournment proposal.

Q: How does the per share merger consideration compare to the market price of Altair common stock prior to announcement of the merger?

A: The merger consideration of $113.00 per share represents a premium of approximately 19% to the closing price of the Class A common stock on October 21, 2024, the last trading day prior to media speculation regarding a potential acquisition of Altair by Siemens Industry; approximately 23% to the 6-month volume weighted average closing price of the Class A common stock for the period ending October 21, 2024; and approximately 51% to the closing price of the Class A common stock on December 21, 2023, the last trading day prior to the leak regarding the acquisition of Ansys by Synopsys. The closing price of Class A common stock on Nasdaq on December 17, 2024, the most recent practicable date prior to the date of this proxy statement, was $106.85 per share. You are encouraged to obtain current market prices of Class A common stock in connection with voting your shares of Altair common stock.

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Q: What will happen in the merger?

A: Pursuant to the merger agreement, Merger Sub will merge with and into Altair, with Altair surviving the merger as a wholly owned subsidiary of Siemens Industry. After the merger, Altair’s securities will be delisted from Nasdaq and deregistered under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and, as a result, Altair will no longer be a publicly held company.

Q: Who will own Altair after the merger?

A: Immediately following the merger, Altair will be a wholly owned subsidiary of Siemens Industry.

Q: What will I receive in the merger?

A: At the effective time of the merger (the “effective time”), you will be entitled to receive, for each share of Altair common stock that you hold immediately prior to the effective time (other than (x) shares held by Altair as treasury stock or held by Siemens Industry, Merger Sub or any other subsidiary of Siemens Industry (collectively, the “excluded shares”) and (y) shares of Altair common stock with respect to which appraisal rights are properly demanded and not withdrawn or lost ( “dissenting shares”) under the DGCL), $113.00 in cash, without interest and subject to any applicable withholding taxes. For example, if you own 100 shares of Altair common stock, you will receive $11,300.00 in cash in exchange for your shares of Altair common stock, without interest and subject to any applicable withholding taxes. You will not be entitled to receive shares of the surviving corporation or Siemens Industry.

Shares of Altair common stock subject to stock-based awards will be treated in the manner described under the heading “The Merger (Proposal 1)—Interests of Altair’s Directors and Executive Officers in the Merger.”

Q: What will happen in the merger to Altair equity awards?

A: Pursuant to the merger agreement, at or immediately prior to the effective time, the outstanding equity awards of Altair will be treated as follows:

Each vested option and each director option that is outstanding and unexercised as of immediately prior to the effective time, in each case, will vest (to the extent unvested) and be canceled and converted into the right to receive an amount in cash (without interest) equal to (x) the number of shares of Class A common stock subject to such vested option or director option immediately prior to the effective time multiplied by (y) the excess of the merger consideration over the per share exercise price applicable to such vested option or director option, less any applicable withholding taxes.

Each unvested option that is outstanding and unexercised as of immediately prior to the effective time will be canceled and converted into the right to receive a future amount in cash equal to (x) the number of shares of Class A common stock subject to such unvested option immediately prior to the effective time multiplied by (y) the excess of the merger consideration over the per share exercise price applicable to such unvested option, which cash award will continue to vest following the effective time, subject to the holder’s continued employment or service through the last day of the calendar quarter preceding the quarter in which such unvested option would have otherwise vested in accordance with the vesting schedule in effect immediately prior to the effective time (had the holder remained in continuous employment or service through such date), and will be paid less any applicable withholding taxes by the surviving corporation or its applicable subsidiary as soon as reasonably practicable but no later than the next regularly scheduled payroll run of the surviving corporation or its applicable subsidiary that is at least ten business days following the applicable vesting date. Notwithstanding the foregoing, such cash award will (i) accelerate in full and be paid upon a holder’s termination without “cause” (as determined by the surviving corporation) or for “good reason” (to the extent such holder has an agreement or participates in an Altair plan that provides for severance benefits upon a resignation for good reason, and as defined in such agreement or Altair plan) and (ii) accelerate upon any other circumstances set forth in any

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applicable award agreement, severance agreement or other similar agreement or Altair plan applicable to the holder as of October 30, 2024 (or entered into between October 30, 2024 and the effective time in accordance with the merger agreement), in each case, subject to the holder’s execution of a release of claims in a form prescribed by the surviving corporation. Such cash award will be forfeited without payment upon the holder’s termination of employment or service with the surviving corporation and its subsidiaries for any reason not described in the preceding sentence.

Each stock option of Altair that has a per share exercise price that is equal to or greater than the merger consideration (if any) will be canceled without payment.

Each vested RSUs and each director RSU will vest (to the extent unvested) and be canceled and converted into the right to receive an amount in cash equal to (x) the number of shares of Class A common stock subject to such vested RSU or director RSU immediately prior to the effective time multiplied by (y) the merger consideration, less any applicable withholding taxes.

Each unvested RSU will be canceled and converted into the right to receive a future amount in cash equal to (x) the number of shares of Class A common stock subject to such unvested RSU immediately prior to the effective time multiplied by (y) the merger consideration, which cash award will continue to vest, subject to the holder’s continued employment or service through the last day of the calendar quarter preceding the quarter in which such unvested RSU would have otherwise vested in accordance with the vesting schedule in effect immediately prior to the effective time (had the holder remained in continuous employment or service through such date), and will be paid less any applicable withholding taxes by the surviving corporation or its applicable subsidiary as soon as reasonably practicable no later than the next regularly scheduled payroll run of the surviving corporation or its applicable subsidiary that is at least ten business days following the applicable vesting date. Notwithstanding the foregoing, such cash award will (i) accelerate in full and be paid upon a holder’s termination without “cause” (as determined by the surviving corporation) or for “good reason” (to the extent the holder has an agreement or participate in an Altair plan that provides for severance benefits upon a resignation for good reason, and as defined in such agreement or Altair plan) and (ii) accelerate upon any other circumstances set forth in any applicable award agreement, severance agreement or other similar agreement or Altair plan applicable to the holder as of October 30, 2024 (or entered into between October 30, 2024 and the effective time in accordance with the merger agreement), in each case, subject to the holder’s execution of a release of claims in a form prescribed by the surviving corporation. Such cash award will be forfeited without payment upon the holder’s termination of employment or service with the surviving corporation and its subsidiaries for any reason not described in the preceding sentence.

For additional information on the treatment of Altair equity awards in connection with the merger, see the section titled “The Merger Agreement—Treatment of Altair Equity Awards.”

Q: Am I entitled to exercise appraisal rights instead of receiving the merger consideration for my shares of Altair common stock?

A: Yes. Altair stockholders are entitled to appraisal rights under Section 262 of the DGCL in connection with the merger, provided they follow the procedures and satisfy the conditions set forth in Section 262 of the DGCL. For more information regarding appraisal rights, see the sections titled “The Merger (Proposal 1)—Appraisal Rights of Altair Stockholders” and “Appraisal Rights of Altair Stockholders.” In addition, a copy of Section 262 of the DGCL is attached as Annex F to this proxy statement. Failure to strictly comply with Section 262 of the DGCL may result in your waiver of, or inability to, exercise appraisal rights.

Q: How many votes do I have?

A: In connection with each matter to be voted upon at the special meeting, each share of Class A common stock owned as of the close of business on the record date is entitled to one vote and each share of Class B common stock owned of record as of the close of business on the record date is entitled to ten votes.

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Q: What vote is required to adopt the merger agreement?

A: The votes required for each proposal are as follows:

1. Proposal 1—The Merger Agreement Proposal: The affirmative vote of holders of at least a majority of the voting power of all outstanding shares of Altair common stock entitled to vote thereon is required to approve the merger agreement proposal.

2. Proposal 2—The Merger-Related Compensation Proposal: The affirmative vote of holders of at least a majority of the voting power of the shares of Altair common stock present in person (virtually) or represented by proxy at the special meeting and entitled to vote thereon is required to approve, on an advisory (non-binding) basis, the merger-related compensation proposal.

3. Proposal 3—The Adjournment Proposal: The affirmative vote of holders of at least a majority of the voting power of the shares of Altair common stock present in person (virtually) or represented by proxy at the special meeting and entitled to vote thereon is required to approve the adjournment proposal.

As of December 17, 2024, the record date, Altair directors and executive officers, as a group, owned and were entitled to vote 369,272 shares of Class A common stock and 16,867,792 shares of Class B common stock or approximately 53.8% of the voting power of all outstanding shares of Altair common stock. Altair currently expects that these directors and executive officers will vote their shares in favor of the merger agreement proposal and each of the other proposals described in this proxy statement, although none of them are obligated to do so other than James R. Scapa pursuant to the terms of the voting agreement. See the section titled “The Voting Agreement.”

Q: Do any of Altair’s directors or officers have interests in the merger that may differ from or be in addition to my interests as a stockholder?

A: In considering the recommendation of the Altair board of directors with respect to the merger agreement proposal, you should be aware that Altair’s directors and executive officers have certain interests in the merger that may be different from, or in addition to, the interests of Altair stockholders generally. The Altair board of directors was aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement and the merger, and in recommending that the merger agreement be approved by the Altair stockholders. See the section titled “The Merger (Proposal 1)—Interests of Altair’s Directors and Executive Officers in the Merger” and “Advisory Vote on Named Executive Officer Merger-Related Compensation Arrangements (Proposal 2).”

Q: When do you expect the merger to be completed?

A: In order to complete the merger, Altair must obtain the stockholder approval of the merger agreement proposal described in this proxy statement and the other closing conditions under the merger agreement must be satisfied or waived (as permitted by applicable law). The parties to the merger agreement currently expect to complete the merger in the second half of 2025, although neither party can assure completion by any particular date, if at all. Because the merger is subject to a number of conditions, the exact timing of the merger cannot be determined at this time.

Q: What conditions must be satisfied to complete the merger?

A: Each party’s obligation to complete the merger is subject to the satisfaction or waiver (to the extent permitted under applicable law) of certain customary mutual conditions, including the following: (i) receipt of stockholder approval, (ii) the absence of any order or law issued by any governmental authority of competent jurisdiction prohibiting, rendering illegal or enjoining the consummation of the merger, (iii) the expiration or termination of all waiting periods (and any extensions thereof) applicable to the consummation of the merger under the HSR

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Act and any commitment to, or agreement with, any governmental authority to delay or not consummate before a certain date the merger and (iv) the receipt of the other required regulatory approvals (as defined in the section titled “The Merger and Merger Agreement—Regulatory Clearances and Approvals Required for the Merger”).

The obligation of each party to consummate the merger is also conditioned upon (i) performance and compliance by the other party in all material respects with its covenants, obligations and agreements required to be performed or complied with by it under the merger agreement prior to the closing of the merger; (ii) the accuracy of the representations and warranties of the other party as of closing (subject to the materiality standards set forth in the merger agreement); and (iii) delivery of an officer certificate by the other party certifying satisfaction of certain of the conditions described above. The obligation of Siemens Industry to consummate the merger is also subject to there not having occurred since October 30, 2024, an Altair material adverse effect (as defined in the section titled “The Merger Agreement—Material Adverse Effect”) that is continuing. Consummation of the merger is not subject to any financing condition.

For additional details regarding conditions to the completion of the merger, see the section titled “The Merger Agreement—Conditions to the Merger.”

Q: Why am I being asked to consider and act upon a proposal to approve, on a non-binding, advisory basis, certain compensation that will or may be paid by Altair to its named executive officers that is based on or otherwise relates to the merger?

A: Section 14A of the Exchange Act requires Altair to seek a non-binding, advisory vote to approve any agreements or understandings and compensation that will or may be paid by Altair to its named executive officers that is based on or otherwise relates to the merger. Approval of this proposal by Altair stockholders is not required to complete the merger.

Q: Do you expect the merger to be taxable to Altair stockholders?

A: The receipt of cash in exchange for Altair common stock pursuant to the merger generally will be a taxable transaction for U.S. federal income tax purposes. U.S. Holders generally will recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference, if any, between (a) the amount of cash received and (b) the U.S. Holder’s adjusted tax basis in the Altair common stock surrendered in exchange. Except in certain specific circumstances described below and under “Material U.S. Federal Income Tax Consequences of the Merger—Non-U.S. Holders,” Non-U.S. Holders generally will not be subject to U.S. federal income tax unless such Non-U.S. Holder has certain connections with the United States.

The U.S. federal income tax consequences described above may not apply to all holders of Altair common stock. You should read the section titled “Material U.S. Federal Income Tax Consequences of the Merger” for a more complete discussion of the U.S. federal income tax consequences of the merger. Tax matters can be complicated and the tax consequences of the merger to you will depend on your particular tax situation. You should consult your tax advisor to determine the applicable U.S. federal, state, local and non-U.S. tax consequences of the merger to you.

Q: Who is entitled to vote at the special meeting?

A: Only Altair stockholders who held shares of record as of the close of business on December 17, 2024, the record date for the special meeting, are entitled to receive notice of and to vote at the special meeting. Altair’s official stock ownership records will conclusively determine whether a stockholder is a “holder of record” as of the close of business on the record date. Participating stockholders who log-on to the special meeting using their unique 16-digit control number will also be able to examine the stockholder list during the special meeting by following the instructions provided on the meeting website at www.virtualshareholdermeeting.com/ALTAIR2025SM.

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Each share of Class A common stock is entitled to one vote on each proposal and each share of Class B common stock is entitled to ten votes on each proposal.

As of the close of business on the record date, there were 60,137,617 shares of Class A common stock outstanding and 25,393,574 shares of Class B common stock outstanding. Class A common stock and Class B common stock will vote as a single class on all matters described in this proxy statement.

Q: Who may attend the special meeting?

A: Only Altair stockholders as of the close of business on December 17, 2024, or their duly appointed proxies, and invited guests of Altair may attend the meeting. “Street name” holders (those whose shares are held through a broker, bank or other nominee) who wish to vote at the special meeting must obtain a proxy, executed in their favor, from their broker, bank or other nominee giving them the right to vote their shares at the special meeting. Altair has retained Broadridge Financial Solutions to host our virtual annual meeting and to distribute, receive, count and tabulate proxies.

Q: Who is soliciting my vote?

A: The Altair board of directors is soliciting your proxy, and Altair will bear the cost of soliciting proxies. Solicitation initially will be made by mail. Some of our officers also may, but without compensation other than their regular compensation, solicit proxies by mail or personal conversations, or by telephone, facsimile or other electronic means. Altair will also, upon request, reimburse brokers and other persons holding stock in their names, or in the names of nominees, for their reasonable out-of-pocket expenses related to forwarding proxy materials to the beneficial owners of Altair common stock and obtaining proxies.

Q: What do I need to do now?

A: After carefully reading and considering the information contained in this proxy statement, please submit your proxy as soon as possible so that your shares of Altair common stock will be represented and voted at the special meeting. Please follow the instructions set forth on the proxy card or on the voting instruction card provided by the record holder if your shares are held in “street name” by your bank, brokerage firm or other nominee.

Q: How do I vote if my shares are registered directly in my name?

A: If you are a stockholder of record, you may vote virtually at the special meeting or vote by proxy using one of the methods described below. Whether or not you plan to participate in the meeting, we urge you to vote by proxy to ensure your vote is counted. You may still participate in the special meeting and vote virtually even if you have already voted by proxy.

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Whether or not you plan to attend the meeting, we urge you to vote by proxy, whether by internet, by telephone or by mail, to ensure your vote is counted. You may still attend the meeting virtually and vote your shares, even if you have already voted by proxy. If you later decide to vote at the special meeting, your proxy submitted prior to the special meeting will be revoked; however, attending the special meeting will not revoke your written, internet or telephone proxy, as the case may be, unless you specifically request revocation or cast a ballot at the special meeting. Please choose only one method to cast your vote by proxy. We encourage you to vote over the internet, which is a convenient, cost-effective and reliable alternative compared to returning a proxy card by mail.

Q: How do I vote if my shares are held in the name of my broker (street name)?

A: If your shares are held in “street name” by your bank, brokerage firm or other nominee, you must direct your bank, brokerage firm or other nominee on how to vote and you will receive instructions from your bank, brokerage firm or other nominee describing how to vote your shares of Altair common stock. The availability of internet or telephonic voting will depend on the nominee’s voting process. Please check with your bank, brokerage firm or other nominee and follow the voting procedures your bank, brokerage firm or other nominee provides.

In accordance with the rules of the New York Stock Exchange, as followed by Nasdaq, your bank, brokerage firm or other nominee can vote your shares of Altair common stock on “routine” matters when they have not received voting instructions from you. However, such banks, brokerage firms and other nominees are precluded from exercising their voting discretion with respect to “non-routine” matters. If you are a beneficial owner and you do not provide these instructions, a “non-vote” occurs with respect to those matters. All proposals described in this proxy to be voted on at the special meeting are considered “non-routine” matters. Accordingly, if you are a beneficial holder and you do not provide your bank, brokerage firm or other nominee instructions on how to vote your shares of Altair common stock at the special meeting, your bank, brokerage firm or other nominee generally will not be permitted to vote your shares on any of the proposals at the special meeting. Such non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the special meeting and will be the same as a vote “AGAINST” the merger agreement proposal, but will not have an effect on the adjournment proposal or the merger-related compensation proposal (assuming, in the case of the merger-related compensation proposal, a quorum is present). If you are a beneficial holder, Altair strongly encourages you to provide voting instructions to your bank, brokerage firm or other nominee so that your vote will be counted on all matters.

Q: Can I change my vote after I submit my proxy?

A: Yes. You can change or revoke your proxy at any time before the final vote at the special meeting or any adjournment or postponement thereof. If you are the record holder of your shares, you may change or revoke your proxy in any one of three ways:

If your shares are held by your broker, bank or other nominee, you will have to follow the instructions provided by your broker, bank or other nominee to change or revoke your proxy.

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Q: What is a proxy?

A: A proxy is your legal designation of another person to vote your shares of Altair common stock. The written document describing the matters to be considered and voted on at the special meeting is called a “proxy statement.” The document used to designate a proxy to vote your shares of Altair common stock is called a “proxy card.” The Altair board of directors has designated James R. Scapa as proxy for the special meeting.

Q: What happens if I sell my shares of Altair common stock before the special meeting?

A: If you transfer your shares after the record date but before the special meeting, you will retain the right to vote such shares at the special meeting, but you will have transferred the right to receive the merger consideration to the person to whom you transfer your shares. In order to receive the merger consideration, you must hold your shares of common stock through completion of the merger.

Q: What happens if I sell my shares of Altair common stock after the special meeting but before the effective time?

A: If you transfer your shares before the record date, you will not have the right to vote such shares at the special meeting and will have transferred the right to receive the merger consideration to the person to whom you transferred your shares. If you transfer your shares after the special meeting but before the effective time, you will have transferred the right to receive the merger consideration to the person to whom you transfer your shares. In order to receive the merger consideration, you must hold your shares of Altair common stock through completion of the merger.

Q: How many shares must be present to constitute a quorum for the meeting?

A: Holders of a majority of the voting power of all issued and outstanding shares of Altair common stock as of the close of business on the record date and entitled to vote at the special meeting must be present or represented by proxy at the special meeting to constitute a quorum for the transaction of business at the special meeting. If you fail to submit a proxy or to vote at the special meeting, or fail to instruct your bank, brokerage firm or other nominee how to vote, your shares of Altair common stock will not be counted towards a quorum. “Broker non-votes” (as described in further detail below), if any, will not be treated as present for purposes of determining whether a quorum is present. Marks to “ABSTAIN” on any proposal are considered present for purposes of establishing a quorum.

Q: What if I abstain from voting?

A: If you attend the special meeting or send in your signed proxy card, but abstain from voting on any proposal, your shares will still be counted for purposes of determining whether a quorum exists, but it will have the same effect as a vote “AGAINST” such proposal.

Q: Will my shares be voted if I do not sign and return my proxy card or vote over the internet, by mail, by telephone or by attendance in person (virtually) at the special meeting?

A: If you are a registered stockholder and you do not sign and return your proxy card by mail or vote over the internet, by telephone or by attendance in person (virtually) at the special meeting, your shares will not be voted at the special meeting and will not be counted for purposes of determining whether a quorum exists. If you are a beneficial owner of shares held in “street name” by your bank, brokerage firm or other nominee, you should have received a voting instruction card with these proxy materials from that organization rather than from Altair. Follow the instructions from your bank, brokerage firm or other nominee to see which of the above choices are available to you to ensure that your vote is counted. To vote virtually at the special meeting, you must obtain a “legal proxy” from your bank, brokerage firm or other nominee.

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If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to vote with respect to the merger agreement proposal, it will have the same effect as a vote “AGAINST” such proposal. If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to vote with respect to merger-related compensation proposal or the adjournment proposal, it will have no effect on the outcome of such proposal (assuming, in the case of the merger-related compensation proposal, a quorum is present).

Q: What is a broker non-vote?

A: A so-called “broker non-vote” results when banks, brokerage firms and other nominees return a valid proxy but do not vote on a particular proposal because they do not have discretionary authority to vote on the matter and have not received specific voting instructions from the beneficial owner of those shares. Broker non-votes count toward a quorum only if at least one proposal is presented with respect to “routine” matters to which the bank, brokerage firm or other nominee has discretionary authority. All proposals described in this proxy statement to be voted on at the special meeting are considered “non-routine” matters, and, therefore, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the special meeting. The effect of not instructing your broker how you wish your shares to be voted will be the same as a vote “AGAINST” the merger agreement proposal, but will not have an effect on the adjournment proposal or the merger-related compensation proposal (assuming, in the case of the merger-related compensation proposal, a quorum is present).

Q: Will my shares held in “street name” or another form of record ownership be combined for voting purposes with shares I hold of record?

A: No. Because any shares you may hold in “street name” will be deemed to be held by a different stockholder than any shares you hold of record, any shares so held will not be combined for voting purposes with shares you hold of record. Similarly, if you own shares in various registered forms, such as jointly with your spouse, as trustee of a trust or as custodian for a minor, you will receive, and will need to sign and return, a separate proxy card for those shares because they are held in a different form of record ownership. Shares held by a corporation or business entity must be voted by an authorized officer of the entity. Shares held in an individual retirement account must be voted under the rules governing the account.

Q: What does it mean if I receive more than one set of proxy materials?

A: You may receive more than one set of voting materials for the special meeting, including multiple copies of this proxy statement and multiple proxy cards or voting instruction cards. For example, if you hold your shares of Altair common stock in more than one brokerage account, you will receive a separate voting instruction card for each brokerage account in which you hold shares. If you are a stockholder of record and your shares are registered in more than one name, you will receive more than one proxy card. Please submit each separate proxy card or voting instruction card that you receive by following the instructions set forth in each separate proxy card or voting instruction card.

Q: Who will count the votes?

A: A representative from Broadridge Financial Solutions will serve as the inspector of election.

Q: Can I participate if I am unable to attend the special meeting?

A: If you are unable to attend the virtual special meeting, you may participate by completing, signing, dating and returning your proxy card or by voting over the internet, by telephone or by mail.

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Q: Where can I find the voting results of the special meeting?

A: Altair intends to announce preliminary voting results at the special meeting and publish final results in a Current Report on Form 8-K that will be filed with the SEC following the special meeting. All reports that Altair files with the SEC are publicly available when filed. For more information, see the section titled “Where You Can Find More Information.”

Q: What happens if the merger is not completed?

A: If the merger agreement is not adopted by Altair stockholders or if the merger is not completed for any other reason, Altair stockholders will not receive any consideration for their shares of Altair common stock in connection with the merger. Instead, Altair will remain an independent public company, Altair common stock will continue to be listed and traded on Nasdaq and registered under the Exchange Act and Altair will continue to file periodic reports with the SEC. Under certain specific circumstances, Altair is required to pay Siemens Industry a termination fee of $372,000,000 and, under certain other specific circumstances, Siemens Industry is required to pay Altair a termination fee of $638,000,000. See section titled “The Merger Agreement—Termination Fees and Expenses.”

For additional information on what happens if the merger is not consummated, see the section titled “The Merger (Proposal 1)—Effect on Altair if the Merger is Not Completed.”

Q: How can I obtain additional information about Altair?

A: Altair will provide copies of this proxy statement and its most recent Annual Report to Stockholders, including its Annual Report on Form 10-K, without charge to any stockholder who makes a written request to our Chief Legal Officer at Altair Engineering Inc., 1820 East Big Beaver Road, Troy, Michigan 48083. Altair’s Annual Report on Form 10-K and other SEC filings may also be accessed at www.sec.gov or on the Investor Relations section of Altair’s website at www.altair.com. Altair’s website address is provided as an inactive textual reference only. The information provided on or accessible through our website is not part of this proxy statement and is not incorporated by reference in this proxy statement by this or any other reference to our website provided in this proxy statement.

Q: How many copies of this proxy statement and related voting materials should I receive if I share an address with another stockholder?

A: The SEC has adopted rules that permit companies and intermediaries, such as brokers, to satisfy the delivery requirements for proxy statements and annual reports with respect to two or more stockholders sharing the same address by delivering a single annual report or proxy statement, as applicable, addressed to those stockholders. This process, which is commonly referred to as “householding,” potentially provides extra convenience for stockholders and cost savings for companies.

Altair and some brokers may be householding our proxy materials by delivering proxy materials to multiple stockholders who request a copy and share an address, unless contrary instructions have been received from the affected stockholders. Once you have received notice from your broker or us that they or we will be householding materials to your address, householding will continue until you are notified otherwise or until you revoke your consent. If at any time you no longer wish to participate in householding and would prefer to receive a separate proxy statement and annual report, please notify your broker if your shares are held in a brokerage account or Altair if you are a stockholder of record. You can notify us by sending a written request to Altair Engineering Inc., 1820 East Big Beaver Road, Troy, Michigan, 48083, Attention: Chief Legal Officer, or calling (248) 614-2400 x453. Stockholders who share a single address, but receive multiple copies of this proxy statement, may request that in the future they receive a single copy by notifying Altair at the telephone number or address set forth in the prior sentence. In addition, Altair will promptly deliver, upon written or oral request to the address or telephone number above, a separate copy of this proxy statement to a stockholder at a shared address to which a single copy of the documents was delivered pursuant to a prior request. If you would like to view the special meeting materials via the internet, please visit www.proxydocs.com/ALTR.

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Q: Who should I contact if I have any questions?

A: If you have any questions about the special meeting, the merger, the proposals or this proxy statement, would like additional copies of this proxy statement, need to obtain proxy cards or other information related to this proxy solicitation or need help submitting a proxy or voting your shares of Altair common stock, you should contact:

Altair Engineering Inc.

Attention: Chief Legal Officer

1820 East Big Beaver Road

Troy, Michigan, 38083

(248) 614-2400 x453

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement and the documents incorporated by reference into this proxy statement contain forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Any statements contained in this proxy statement that are not statements of historical fact, including statements regarding the merger, including the expected timing and closing of the merger; Altair’s ability to consummate the merger; the expected benefits of the merger and other considerations taken into account by the board of directors of Altair in approving the merger; and the amounts to be received by stockholders and expectations for Altar prior to and following the closing of the merger, may be deemed to be forward-looking statements. All such forward-looking statements are intended to provide management’s current expectations for the future of Altair based on current expectations and assumptions relating to Altair’s business, the economy and other future conditions. Forward-looking statements generally can be identified through the use of words such as “believes,” “anticipates,” “may,” “should,” “will,” “plans,” “projects,” “expects,” “expectations,” “estimates,” “forecasts,” “predicts,” “targets,” “prospects,” “strategy,” “signs,” and other words of similar meaning in connection with the discussion of future performance, plans, actions or events.

Because forward-looking statements relate to the future, they are subject to inherent risks, uncertainties and changes in circumstances that are difficult to predict. Such risks and uncertainties include, among others:

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Altair cautions that the foregoing list of factors is not exhaustive. Additional information concerning these and other risk factors is contained in Altair’s most recently filed Annual Report on Form 10-K for the year ended December 31, 2023 and subsequently filed Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other SEC filings, as such filings may be amended from time to time. All of the forward-looking statements made by Altair contained or incorporated by reference in this proxy statement and all subsequent written and oral forward-looking statements concerning Altair, the merger or other matters attributable to Altair or any person acting on its behalf are expressly qualified in their entirety by the cautionary statement above.

If any of these risks materialize or any of Altair’s assumptions prove incorrect, actual results could differ materially from the results implied by these forward-looking statements. There may be additional risks that Altair presently does not know of or that Altair currently believes are immaterial that could also cause actual results to differ from those contained in the forward-looking statements. In addition, forward-looking statements reflect Altair’s expectations, plans or forecasts of future events and views as of the date of this proxy statement. Altair anticipates that subsequent events and developments will cause Altair’s assessments to change. However, while Altair may elect to update these forward-looking statements at some point in the future, Altair specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing Altair’s assessments as of any date subsequent to the date of this proxy statement. Accordingly, reliance should not be placed upon the forward-looking statements.

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THE COMPANIES

Altair Engineering Inc.

Altair Engineering Inc. is a global leader in computational science and artificial intelligence enabling organizations across broad industry segments to drive smarter decisions in an increasingly connected world. Altair delivers software and cloud solutions in the areas of simulation and design, high-performance computing, data analytics, and artificial intelligence. Altair’s products and services leverage computational intelligence to drive innovation for a more connected, safe, and sustainable future. Altair was incorporated in the state of Delaware on October 6, 2017, shortly before the consummation of its initial public offering. The Class A common stock trades on the Nasdaq Global Select Market under the symbol “ALTR.” The principal executive offices of Altair are located at 1820 East Big Beaver Road, Troy, Michigan, 48083, and its telephone number is (248) 614-2400.

Siemens Aktiengesellschaft

Siemens Aktiengesellschaft (Berlin and Munich) (“Siemens AG” or “Guarantor”), a German stock corporation and the ultimate parent company of Siemens Industry, is a leading technology company focused on industry, infrastructure, mobility, and healthcare. The company’s purpose is to create technology to transform the everyday, for everyone. By combining the real and the digital worlds, Siemens empowers customers to accelerate their digital and sustainability transformations, making factories more efficient, cities more livable, and transportation more sustainable. Siemens also owns a majority stake in the publicly listed company Siemens Healthineers, a leading global medical technology provider pioneering breakthroughs in healthcare. For everyone. Everywhere. Sustainably. Siemens AG was incorporated in Germany in 1847. The shares of Siemens AG common stock trade on the Börse Frankfurt under the symbol “SIE.”

Siemens AG’s principal executive office is located at Werner-von-Siemens-Straße 1, 80333 Munich, Federal Republic of Germany. Siemens AG’s corporate website address is https://www.Siemens.com/global/en.html. Siemens AG’s telephone number is +49 (89) 3803 5491. The information provided on Siemens AG’s website is not part of this proxy statement and is not incorporated in this proxy statement by reference by this or any other reference to its website provided in this proxy statement.

Siemens Industry Software Inc.

Siemens Industry Software Inc. (“Siemens Industry”) is a Delaware corporation and an indirect subsidiary of Siemens AG. Siemens Industry and its global affiliates offer production, supply chain, and product lifecycle management software, including software for simulation and testing of mechatronic systems, Electronic Design Automation software, the SupplyFrame supply chain management software, and an open, cloud-based industrial internet of things operating system, Insights Hub, which connects machines and physical infrastructure to the digital world. Siemens Industry’s principal executive office is located at 5800 Granite Parkway, Suite 600, Plano, Texas, 75024. Siemens Industry’s telephone number is (800) 498-5351. Siemens Industry’s internet website address is https://www.sw.siemens.com. The information provided on Siemens Industry’s website is not part of this proxy statement and is not incorporated in this proxy statement by reference by this or any other reference to its website provided in this proxy statement. Upon completion of the merger, Altair will be a wholly owned subsidiary of Siemens Industry.

Astra Merger Sub

Astra Merger Sub Inc., a Delaware corporation, is a wholly owned subsidiary of Siemens Industry. Merger Sub was incorporated by Siemens Industry solely in contemplation of the transactions contemplated by the merger agreement, has not conducted any business and has no assets, liabilities or obligations of any nature other than as set forth in the merger agreement. The principal executive offices of Merger Sub are located at c/o Siemens Industry Software Inc., 5800 Granite Parkway, Suite 600, Plano, Texas, 75024, and Merger Sub’s telephone number is (800) 498-5351.

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THE SPECIAL MEETING

General

This proxy statement is first being mailed on or about December 18, 2024, and constitutes notice of the special meeting in conformity with the requirements of the DGCL and Altair’s bylaws.

This proxy statement is being provided to Altair stockholders as part of a solicitation of proxies by the Altair board of directors for use at the special meeting of Altair stockholders and at any adjournments or postponements of such special meeting. This proxy statement provides Altair stockholders with information about the special meeting and should be read carefully in its entirety.

Date, Time and Place of the Special Meeting

The special meeting will be held on January 22, 2025, beginning at 10:00 a.m., Eastern Time, unless postponed to a later date, via live audio webcast at www.virtualshareholdermeeting.com/Altair2025SM. To virtually participate in the special meeting, visit such website and enter the 16-digit control number provided on your proxy card or voting instruction card in order to participate in the special meeting.

Purposes of the Special Meeting

At the special meeting, Altair stockholders will be asked to vote upon the following proposals:

Only the approval of the merger agreement proposal is required for completion of the merger. Altair will transact no other business at the special meeting except such business as may properly be brought before the special meeting or any adjournment or postponement thereof.

Recommendation of the Altair Board of Directors

At a special meeting of the Altair board of directors held on October 30, 2024, the Altair board of directors unanimously determined that the merger agreement and the transactions contemplated thereby are advisable, fair to and in the best interests of Altair and Altair stockholders, approved the execution of the merger agreement and the consummation of the transactions contemplated thereby, and directed that the adoption of the merger agreement be submitted to a vote at a meeting of the Altair stockholders.

Accordingly, the Altair board of directors unanimously recommends that Altair stockholders vote (1) “FOR” the merger agreement proposal, (2) “FOR” the merger-related compensation proposal and (3) “FOR” the adjournment proposal.

Altair stockholders should carefully read this proxy statement, including any documents incorporated by reference, and the annexes in their entirety for more detailed information concerning the merger and the transactions contemplated by the merger agreement.

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Virtual Participation at Special Meeting

The special meeting will be a completely virtual meeting of stockholders conducted via live audio webcast through the website described above under the heading “Date, Time and Place of the Special Meeting.”

Altair will have technicians ready to assist Altair stockholders with any technical difficulties they may have accessing the virtual meeting. If Altair stockholders encounter any difficulties accessing the virtual meeting or during the meeting time, Altair stockholders should navigate to www.virtualshareholdermeeting.com/Altair2025SM, where a phone number for IT support will be posted.

Outstanding Shares as of the Record Date

As of the close of business on the record date, there were 60,137,617 shares of Class A common stock outstanding and 25,393,574 shares of Class B common stock outstanding, owned by Altair stockholders (i.e., excluding shares of Altair common stock held in treasury by Altair). Each share of Class A common stock is entitled to one vote on each matter considered at the special meeting and each share of Class B common stock is entitled to ten votes on each matter considered at the special meeting. The Class A common stock and Class B common stock will vote as a single class on all matters considered at the special meeting.

Stockholders may request an appointment to inspect a complete list of stockholders entitled to vote at the special meeting for any purpose germane to the special meeting at Altair’s principal executive offices located at 1820 East Big Beaver Road, Troy, Michigan 48083, Attention: Chief Legal Officer, during ordinary business hours within ten days prior to the special meeting. This list will also be made available at the special meeting for examination by any stockholder virtually present at the special meeting.

Record Date; Stockholders Entitled to Vote

Only holders of record of Class A common stock and Class B common stock at the close of business on the record date, December 17, 2024, are entitled to receive notice of the special meeting and to vote either class of Altair common stock that they held on the record date at the meeting, or any postponement or adjournment of the meeting. Each share of Class A common stock is entitled to one vote on each proposal and each share of Class B common stock is entitled to ten votes on each proposal. The Class A common stock and Class B common stock will vote as a single class on all matters described in this proxy statement. Altair’s official stock ownership records will conclusively determine whether a stockholder is a “holder of record” as of the close of business on the record date.

Quorum and Broker Non-Votes

Holders of a majority of the voting power of all issued and outstanding shares of Altair common stock as of the close of business on the record date and entitled to vote at the special meeting must be present or represented by proxy at the special meeting to constitute a quorum for the transaction of business at the special meeting. If you fail to submit a proxy or to vote at the special meeting, or fail to instruct your bank, brokerage firm or other nominee how to vote, your shares of Altair common stock will not be counted towards a quorum. Marks to “ABSTAIN” on any proposal are considered present for purposes of establishing a quorum. In the event that a quorum is not present at the special meeting, it is expected that the special meeting will be adjourned or postponed. If the special meeting is postponed or adjourned, it will not affect the ability of holders of record of Altair common stock as of the close of business on the record date to exercise their voting rights or to revoke any previously granted proxy using the methods described below; however, if a new record date is set for an adjourned meeting, a new quorum will be required to be established.

Banks, brokerage firms and other nominees who hold shares in “street name” for the accounts of their clients may vote such shares either as directed by their clients or in their own discretion on “routine” matters. When a broker does not receive instructions from a beneficial owner on how to vote shares with respect to a “non-routine” matter, a “broker non-vote” occurs. “Broker non-votes,” if any, will not be treated as present for

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purposes of determining whether a quorum is present. All proposals described in this proxy statement to be voted on at the special meeting are considered “non-routine” matters. The effect of not instructing your broker how you wish your shares to be voted (i.e., a broker non-vote) will be the same as a vote “AGAINST” the merger agreement proposal, but will not have an effect on the adjournment proposal or the merger-related compensation proposal (assuming, in the case of the merger-related compensation proposal, a quorum is present).

Your shares will be counted for purposes of determining if there is a quorum, whether representing votes for, against or abstained, if you (1) participate in the special meeting or (2) have voted via the internet, by telephone or by properly submitting a proxy card or voting instruction card by mail.

Required Vote; Treatment of Abstentions and Failure to Vote

The votes required for each proposal are as follows:

Proposal 1—The Merger Agreement Proposal: The affirmative vote of holders of at least a majority of the voting power of all outstanding shares of Altair common stock entitled to vote thereon is required to approve the merger agreement proposal. If you mark “ABSTAIN” on your proxy, fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee to vote with respect to the merger agreement proposal, it will have the same effect as a vote “AGAINST” the merger agreement proposal.

Proposal 2—The Merger-Related Compensation Proposal: The affirmative vote of holders of at least a majority of the voting power of the shares of Altair common stock present in person (virtually) or represented by proxy at the special meeting and entitled to vote thereon is required to approve, on an advisory (non-binding) basis, the merger-related compensation proposal. If you mark “ABSTAIN” on your proxy, it will have the same effect as a vote “AGAINST” the merger-related compensation proposal. If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to with respect to the merger-related compensation proposal, it will have no effect on the merger-related compensation proposal (assuming a quorum is present).

Proposal 3—The Adjournment Proposal: The affirmative vote of holders of at least a majority of the voting power of the shares of Altair common stock present in person (virtually) or represented by proxy at the special meeting and entitled to vote thereon is required to approve the adjournment proposal. If you mark “ABSTAIN” on your proxy, it will have the same effect as a vote “AGAINST” the adjournment proposal. If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to vote with respect to the adjournment proposal, it will have no effect on the adjournment proposal.

An abstention occurs when a stockholder attends a meeting, either by attendance in person (virtually) or by proxy, but abstains from voting. At the special meeting, abstentions will be counted in determining whether a quorum is present and will have the effect of a vote “AGAINST” the merger agreement proposal, the merger-related compensation proposal and the adjournment proposal.

If you are a registered stockholder and you do not sign and return your proxy card by mail or vote over the internet, by telephone or by attendance in person (virtually) at the special meeting, your shares will not be voted at the special meeting and will not be counted for purposes of determining whether a quorum exists. If you are the record owner of your shares and you fail to vote, it will have the same effect as a vote “AGAINST” the merger agreement proposal, but will have no effect on the outcome of the merger-related compensation proposal or the adjournment proposal.

Shares and Voting of Altair Directors and Executive Officers

As of the close of business on December 17, 2024, the record date, Altair directors and executive officers, as a group, owned and were entitled to vote 369,272 shares of Class A common stock and 16,867,792 shares of

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Class B common stock or approximately 53.8% of the voting power of all outstanding shares of Altair common stock. Altair currently expects that these directors and executive officers will vote their shares in favor of the merger agreement proposal and each of the other proposals described in this proxy statement, although none of them are obligated to do so other than James R. Scapa pursuant to the terms of the voting agreement. See the section titled “The Voting Agreement.”

How to Vote or Have Your Shares Voted

Altair stockholders of record may vote their shares of Altair common stock or submit a proxy to have their shares of Altair common stock voted at the special meeting in one of the following ways:

Whether or not you plan to participate in the special meeting, Altair urges you to submit your proxy by completing and returning the proxy card as promptly as possible, or by submitting your proxy by telephone or via the internet, prior to the special meeting to ensure that your shares of Altair common stock will be represented and voted at the special meeting if you are unable to participate.

The Altair board of directors has appointed certain persons as proxy holders to vote proxies in accordance with the instructions of Altair stockholders. If you are a stockholder of record and you authorize these proxy holders to vote your shares of Altair common stock with respect to any matter to be acted upon, your shares will be voted in accordance with your instructions in your proxy. If you are a stockholder of record and you authorize these proxy holders to vote your shares but do not specify how your shares should be voted on a proposal, these proxy holders will vote your shares on such proposals as the Altair board of directors recommends. If any other matter properly comes before the special meeting, these proxy holders will vote on that matter in their discretion.

If, as of the close of business on the record date, your shares of Altair common stock are registered directly in your name with the transfer agent of Altair, Equiniti Trust Company, LLC (f.k.a., American Stock Transfer & Trust Company, LLC), you are considered the stockholder of record with respect to those shares. As the stockholder of record, you have the right to vote or to grant a proxy for your vote directly to Altair or to a third party to vote at the special meeting.

If, as of the close of business on the record date, your shares are held in an account at a bank, brokerage firm or other nominee, you are the beneficial owner of shares held in “street name,” and, for the purposes of this proxy statement, a beneficial owner, and your bank, brokerage firm or other nominee is considered the stockholder of record with respect to those shares. If you are a beneficial owner, you have a right to direct your bank, brokerage firm or other nominee on how to vote the shares held in your account. The availability of internet or telephonic voting will depend on the nominee’s voting process. Please check with your bank, brokerage firm or other nominee and follow the voting procedures your bank, brokerage firm or other nominee provides.

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In accordance with the rules of the New York Stock Exchange, as followed by Nasdaq, your bank, brokerage firm or other nominee may generally vote on “routine” matters when they have not received voting instructions from you. However, such banks, brokerage firms and other nominees are precluded from exercising their voting discretion with respect to “non-routine” matters. If you are a beneficial owner and do not provide these instructions, a “non-vote” occurs with respect to those matters. All proposals described in this proxy statement to be voted on at the special meeting are considered “non-routine” matters. Accordingly, if you are a beneficial owner and do not provide your bank, brokerage firm or other nominee instructions on how to vote your shares of Altair common stock, your bank, brokerage firm or other nominee generally will not be permitted to vote your shares on any of the proposals. The effect of not instructing your broker how you wish your shares to be voted will be the same as a vote “AGAINST” the merger agreement proposal but will not have an effect on the adjournment proposal or the merger-related compensation proposal (assuming, in the case of the merger-related compensation proposal, that a quorum is present). If you are a beneficial holder, Altair strongly encourages you to provide voting instructions to your bank, brokerage firm or other nominee so that your vote will be counted on all matters.

If you are a beneficial owner, you are invited to participate in the special meeting; however, you may not vote your shares at the special meeting unless you obtain a “legal proxy” from your bank, brokerage firm or other nominee that holds your shares, giving you the right to vote the shares at the special meeting.

Revocation of Proxies

Altair stockholders of record may revoke their proxies at any time prior to the voting at the special meeting in any of the following ways:

Altair beneficial owners may change their voting instruction only by following the directions received from their bank, brokerage firm or other nominee for changing their voting instructions.

Delivery of Proxy Materials

As permitted by applicable law, only one copy of this proxy statement is being delivered to holders of Altair common stock residing at the same address, unless such holders of Altair common stock have notified Altair of their desire to receive multiple copies of this proxy statement.

Altair will promptly deliver, upon oral or written request, a separate copy of this proxy statement to any holder of Altair common stock residing at an address to which only one copy of this proxy statement was mailed. Requests for additional copies should be directed to Altair by mail at Altair Engineering Inc., Attention: Chief Legal Officer, 1820 East Big Beaver Road, Troy, Michigan 48083 or by calling (248) 614-2400 x 453.

Shares Held in Name of Broker

If your shares are held by your broker, bank or other nominee, often referred to as held in “street name,” you will receive a form from your broker, bank or other nominee seeking instruction as to how your shares should be voted. You should contact your broker, bank or other nominee with questions about how to provide or revoke your instructions.

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Tabulation of Votes

A representative from Broadridge Financial Solutions will serve as the inspector of election.

Solicitation of Proxies

The Altair board of directors is soliciting your proxy and Altair will bear the cost of soliciting proxies. Solicitation initially will be made by mail. Some of our officers also may, but without compensation other than their regular compensation, solicit proxies by mail or personal conversations, or by telephone, facsimile or other electronic means. Altair will also, upon request, reimburse brokers and other persons holding stock in their names, or in the names of nominees, for their reasonable out-of-pocket expenses related to forwarding proxy materials to the beneficial owners of Altair common stock and obtaining proxies.

Adjournments

The special meeting may be adjourned by the holders of shares of Altair common stock representing at least a majority of the voting power of the shares of Altair common stock present in person (virtually) or represented by proxy at the special meeting entitled to be cast, if sufficient votes are cast in favor of adjournment, whether or not there is a quorum.

Notice need not be given of any adjourned meeting if the time and place, if any, thereof and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present and vote at such adjourned meeting are announced at the meeting at which the adjournment is taken unless the adjournment is for more than 30 days, in which case a notice of the adjourned meeting will be given to each stockholder of record entitled to vote at the meeting. If, after any adjournment, a new record date for the stockholders entitled to vote is fixed for any adjourned meeting, notice of the place, if any, date, and time of the adjourned meeting and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present and vote at such adjourned meeting must be given to each stockholder of record entitled to vote at the meeting.

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THE MERGER (PROPOSAL 1)

This section of this proxy statement describes the material aspects of the merger. This section may not contain all of the information that is important to you. You should carefully read this entire proxy statement and the documents incorporated by reference into this proxy statement, including the full text of the merger agreement, a copy of which is attached to this proxy statement as Annex A, for a more complete understanding of the merger. In addition, important information about Altair is included in or incorporated by reference into this proxy statement. See the section titled “Where You Can Find More Information.”

Effects of the Merger

Upon the terms and subject to the conditions set forth in the merger agreement and in accordance with the DGCL, at the effective time, Merger Sub will merge with and into Altair, whereupon the separate existence of Merger Sub will cease, and Altair will survive the merger as a wholly owned subsidiary of Siemens Industry. The merger will become effective at such time when the certificate of merger is duly filed with the Secretary of State of the State of Delaware in accordance with the relevant provisions of the DGCL (or at such later time as may be specified in the certificate of merger).

At the effective time, each share of Altair common stock (including any Altair common stock to the extent issued in accordance with the terms of the merger agreement and the convertible notes indenture, but excluding (i) Altair common stock held by Altair as treasury stock or owned by Siemens Industry, Merger Sub or any other subsidiary of Siemens Industry immediately prior to the effective time and (ii) Altair common stock with respect to which appraisal rights are properly demanded and not withdrawn or lost under the DGCL) outstanding immediately prior to the effective time will automatically be converted into the right to receive $113.00 in cash, without interest.

Pursuant to the merger agreement, immediately prior to the effective time:

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If the merger is completed, Altair’s securities will be delisted from The Nasdaq Global Select Market and deregistered under the Exchange Act as promptly as practicable after the effective time, and Altair will cease to be a publicly traded company. As a result, you will not own any shares of the surviving corporation.

Effect on Altair if the Merger is Not Completed

If the merger agreement is not adopted by Altair’s stockholders or if the merger is not completed for any other reason, Altair stockholders will not receive any payment for their shares of Altair common stock or other Altair equity interests in connection with the merger. Instead, Altair will remain an independent public company, Class A common stock will continue to be listed and traded on the Nasdaq and registered under the Exchange Act and we will continue to file periodic reports with the SEC. In addition, if the merger is not completed, Altair stockholders will continue to be subject to the same risks and opportunities to which they are currently subject, including risks related to the highly competitive industry in which Altair operates and risks related to adverse economic conditions.

Furthermore, if the merger is not completed, and depending on the circumstances that would have caused the merger to not be completed, it is likely that the price of Class A common stock will decline significantly. If

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that were to occur, it is uncertain when, if ever, the price of Class A common stock would return to the price at which it trades as of the date of this proxy statement, the price at which it traded immediately prior to the public announcement of the merger agreement or the price at which it traded immediately prior to the date (October 22, 2024) on which rumors regarding the proposed transaction were reported by persons unrelated to Altair and Siemens Industry. Accordingly, if the merger is not completed, there can be no assurance as to the effect of these risks and opportunities on the future value of your shares of Altair common stock. If the merger agreement is not adopted by Altair stockholders or if the merger is not completed for any other reason, there can be no assurance that any other transaction acceptable to Altair will be offered or that Altair’s business, prospects or results of operation will not be adversely impacted.

Moreover, if the merger is not completed for any reason, Altair stockholders will be subject to a number of risks, including Altair’s incurrence of substantial costs in connection with the merger and the other transactions contemplated by the merger agreement that may not be recovered, the substantial restrictions imposed by the merger agreement on the operation of Altair’s business during the period before the consummation of the merger, which may make it difficult for Altair to achieve its business goals if the merger is not completed, and the potential negative impact on Altair’s ability to attract, hire and retain key employees.

In addition, the merger agreement provides that, upon termination of the merger agreement under certain circumstances, Altair will be required to pay to Siemens Industry a termination fee of $372 million, or under certain other circumstances, Siemens Industry will be required to pay Altair a termination fee of $638 million. See the section titled “The Merger Agreement—Termination Fees and Expenses” for a discussion of the circumstances under which such termination fees would be required to be paid.

Background of the Merger

The following chronology summarizes the key meetings and events that led to the signing of the merger agreement. This chronology does not purport to catalogue every conversation of or among the Altair board of directors, Siemens AG, Siemens Industry, Altair’s representatives, Siemens AG’s representatives, Siemens Industry’s representatives and other parties.

The Altair board of directors and senior management regularly review and assess Altair’s operations, performance, opportunities, prospects and strategic direction. In connection with this review and assessment, and with the assistance of legal and financial advisors, the Altair board of directors and management have considered potential strategic alternatives for Altair, including potential business combinations or other transactions, to strengthen Altair’s business and maximize stockholder value. In addition, Altair has from time to time received unsolicited inquiries from third parties seeking to determine Altair’s interest in a business combination transaction.

Commencing in December 2023, research analyst reports published by the equity research division of various financial institutions suggested that Altair was well-positioned and likely to become an acquisition target following the increase in mergers and acquisitions activity in the industrial software space.

On February 1, 2024, James R. Scapa, the Co-Founder, Chairman and Chief Executive Officer of Altair, met with the Chief Executive Officer of a strategic industry participant (referred to herein as “Party A”) to discuss, at a high level, Party A’s recent strategic initiatives and potential commercial and strategic partnership opportunities between Altair and Party A.

On February 15, 2024, the Altair board of directors held a regularly scheduled meeting at which members of Altair management were present. Among other matters of business, the Altair board of directors discussed recent mergers and acquisitions activity involving certain competitors of Altair and the recent trend towards consolidation within the industrial software industry, as well as the implications for Altair. Following this discussion, the Altair board of directors agreed that it was in the best interests of Altair and its stockholders for Mr. Scapa and Altair management to explore potential strategic opportunities at a high level, including by

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engaging in exploratory discussions, with a view to providing the Altair board of directors with a further update at its next regularly scheduled board meeting.

In early March 2024, a representative of a strategic advisor to Altair arranged a meeting between Mr. Scapa and the Chief Executive Officer of a strategic industry participant (referred to herein as “Party B”) to discuss industry trends and whether there could be an opportunity for a potential strategic transaction involving Altair and Party B. Mr. Scapa and the Chief Executive Officer of Party B met on March 6, 2024 and, over the next several weeks, representatives from both parties continued to discuss at a high level potential strategic opportunities involving Altair and Party B.

On March 22, 2024, Mr. Scapa was introduced to Tony Hemmelgarn, the President and Chief Executive Officer of Siemens Digital Industries Software (a business unit of Siemens AG offering production, supply chain, and product lifecycle management software), and Robert Jones, the Executive Vice President, Global Sales and Customer Support of Siemens Digital Industries Software, by a mutual business contact.

On March 25, 2024, representatives of Altair management and representatives of Party B management held a virtual meeting to discuss potential opportunities for collaboration, including through product partnerships and other potential strategic opportunities involving Altair and Party B.

On March 26, 2024 and April 3, 2024, Mr. Scapa spoke telephonically with the Chief Executive Officer of Party B to continue their previous discussions regarding potential strategic opportunities involving Altair and Party B.

Also on March 26, 2024 and on April 2, 2024, a strategic advisor to Altair spoke telephonically with the Chief Executive Officer and Chief Financial Officer of Party B regarding potential strategic opportunities between Altair and Party B. On April 4, 2024, the same strategic advisor to Altair spoke again with the Chief Executive Officer of Party B, during which conversation the Chief Executive Officer informed the strategic advisor that, while he believed there could be value in a strategic transaction involving Altair and Party B, Party B had other strategic priorities at that time. The Chief Executive Officer of Party B indicated that Party B would like to participate in any formal strategic process that the Altair board of directors may determine to run.

On May 9, 2024, the Altair board of directors held a regularly scheduled meeting at which members of Altair management were present. Among other matters of business, the Altair board of directors discussed the impact of current industry dynamics on Altair and potential strategic responses. Mr. Scapa also updated the Altair board of directors on the substance of the recent conversations between members of Altair management and other strategic industry participants regarding potential strategic opportunities involving Altair and such potential counterparties. Following this discussion, the Altair board of directors reaffirmed their support for Mr. Scapa and Altair management to continue exploring potential strategic opportunities involving Altair and potential strategic counterparties, with a view to Altair management providing the Altair board of directors with a further update at its next meeting.

On May 16, 2024, Mr. Scapa, Mr. Hemmelgarn, Mr. Jones and Stephanie Buckner, Chief Operating Officer of Altair, met to discuss industry trends and potential opportunities for collaboration between Altair and Siemens Industry.

From May 2024 to June 2024, Mr. Scapa, Matthew Brown, Chief Financial Officer of Altair, and Ms. Buckner, held a series of conversations with representatives of Siemens Industry to explore potential strategic opportunities involving Altair and Siemens Industry.

On May 20, 2024, Mr. Brown met with the Chief Financial Officer of Party B to discuss the possibility of a strategic transaction involving Altair and Party B. Party B informed Mr. Brown that, while it viewed a potential strategic transaction involving the two parties as a potentially attractive proposition, Party B was not in a position to proactively prioritize such a strategic transaction at that time.

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On June 13, 2024, Mr. Brown and Ms. Buckner spoke telephonically with Suzanne Kopcha, the Vice President, Strategy of Siemens Digital Industries Software, to answer preliminary questions from Siemens Industry related to potential strategic opportunities involving Altair and Siemens Industry.

On June 18, 2024, at the request of Mr. Hemmelgarn, Mr. Scapa and Mr. Hemmelgarn spoke telephonically to review the state of discussions regarding potential strategic opportunities involving Altair and Siemens Industry.

On July 11, 2024, Mr. Brown spoke telephonically with Ms. Kopcha to answer additional inquiries to help Siemens Industry improve its understanding of Altair’s business. Ms. Kopcha requested an in-person meeting on July 24, 2024 or July 25, 2024 to continue these discussions.

On July 22, 2024, Altair engaged Davis Polk & Wardwell LLP (“Davis Polk”) to serve as Altair’s transaction counsel in connection with Altair’s exploration of potential strategic alternatives, alongside Altair’s existing outside corporate counsel, Lowenstein Sandler LLP (“Lowenstein”).

Also on July 22, 2024, Altair and Siemens AG entered into a mutual non-disclosure agreement to facilitate the exchange of confidential information in connection with the exploration of strategic opportunities involving Altair and Siemens Industry.

On July 25, 2024, Mr. Brown and Ms. Buckner conducted an in-person meeting with representatives of Siemens Industry and Siemens AG to help Siemens Industry and Siemens AG improve their understanding of Altair’s business, during which Mr. Brown and Ms. Buckner provided a general corporate overview of Altair.

On July 26, 2024, members of Altair management contacted representatives of Citi and J.P. Morgan to discuss a variety of strategic alternatives that might be available to Altair and which the Altair board of directors might consider.

On July 28, 2024, the Altair board of directors held a special meeting at which Mr. Brown, Ms. Buckner, Raoul Maitra, the Chief Legal Officer of Altair, and a representative of Lowenstein were also present. Mr. Scapa provided the Altair board of directors with an update on (i) the highly preliminary and exploratory discussions between Altair and Siemens Industry regarding a potential strategic transaction involving Altair and Siemens Industry, (ii) the preliminary conversation between Mr. Scapa and the Chief Executive Officer of Party A and (iii) the high-level discussions between Altair and Party B and Party B’s indication that it was not in a position at that time to proactively prioritize a potential strategic transaction with Altair (without foreclosing the possibility of participating in any formal strategic process that the Altair board of directors determined to run). The Altair board of directors discussed various factors weighing in favor of, and against, engaging in more formal exploratory discussions with Siemens Industry, Party A and Party B. The Altair board of directors then discussed how, if Altair determined to commence a process of evaluating strategic alternatives, such a process would be conducted, including the importance of reaching out to other potentially interested parties. The Lowenstein representative outlined how such a process could proceed and provided an overview of the directors’ fiduciary duties generally and in connection with such a process. Mr. Scapa then relayed to the Altair board of directors the discussion on July 26, 2024 with representatives of Citi and J.P. Morgan regarding potential strategies with respect to the exploration of strategic alternatives, including contacting a select group of strategic counterparties as part of a competitive process. After discussing potential approaches with respect to the exploration of strategic alternatives, the Altair board of directors identified three strategic industry participants (referred to herein as “Party C”, “Party D” and “Party E”), in addition to Party A, Party B and Siemens Industry, that the Altair board of directors determined to be most likely to be interested in a potential strategic transaction with Altair and were believed to have the capacity to engage in a strategic transaction of that size. After further discussion and taking into account certain factors including the importance of confidentiality and a desire to minimize the risk of a potential leak, the Altair board of directors directed Altair management to continue engaging with Siemens Industry and to proceed with targeted outreach to Party B, Party C, Party D and Party E. The Altair board of

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directors then evaluated both Citi’s and J.P. Morgan’s qualifications, credentials and independence, considering, among other things, (i) both firms’ significant familiarity with Altair’s business and industry and experience running strategic processes, (ii) the Altair board of directors’ significant familiarity with both firms and (iii) the existing relationships between Citi or J.P. Morgan, on the one hand, and the potential strategic counterparties (including Siemens Industry), on the other hand. After such evaluation and consideration, the Altair board of directors approved the engagement of Citi and J.P. Morgan as its financial advisors to assist in the strategic process, including entry into engagement letters with each firm.

Between July 30, 2024 and August 1, 2024, at the direction of the Altair board of directors, representatives of Citi and J.P. Morgan initiated outreach to and had preliminary discussions with Party B, Party C, Party D and Party E to solicit their interest in a potential strategic transaction with Altair.

On August 1, 2024, representatives of Citi and J.P. Morgan spoke telephonically with a representative of Party C, who indicated Party C’s desire to meet with Altair management to inform its decision of whether to pursue a potential strategic transaction between Altair and Party C.

Also on August 1, 2024, a representative of Party D contacted representatives of Citi and J.P. Morgan to request a discussion between Mr. Scapa and the Chair of the board of directors of Party D, indicating that Party D would contact Mr. Scapa directly.  

On August 2, 2024, at the direction of the Altair board of directors, Altair entered into an engagement letter with J.P. Morgan as its financial advisor with respect to its exploration of potential strategic alternatives.

Also on August 2, 2024, representatives of Citi and J.P. Morgan spoke telephonically with representatives of Party B, who indicated Party B’s interest in participating in a process to evaluate a potential strategic transaction involving Altair and Party B and Party B’s desire to schedule a meeting with Altair management. Subsequently, on August 2, 2024, representatives of Citi and J.P. Morgan sent a form of non-disclosure agreement to Party B.

On August 6, 2024, a representative of Party C contacted Mr. Scapa to suggest a meeting to discuss a potential strategic transaction between Altair and Party C, though the meeting did not immediately materialize.

On August 7, 2024, at the direction of the Altair board of directors, Altair entered into an engagement letter with Citi as its financial advisor with respect to its exploration of potential strategic alternatives.

On August 9, 2024, Mr. Scapa spoke telephonically with Mr. Hemmelgarn to discuss expectations regarding a second in-person meeting, scheduled for August 13, 2024, involving representatives of Siemens Industry and Siemens AG and Mr. Scapa, Mr. Brown and Ms. Buckner to respond to Siemens Industry’s and Siemens AG’s inquiries regarding Altair’s business and to review the state of discussions among Altair, Siemens Industry and Siemens AG to date.

On August 11, 2024, at the request of Party D, Mr. Scapa contacted a representative of Party D to coordinate a call with the Chair of the board of directors of Party D, which was scheduled for August 18, 2024.

On August 13, 2024, Mr. Scapa, Mr. Brown and Ms. Buckner conducted a second in-person meeting with representatives of Siemens Industry, including Mr. Jones, and Siemens AG to respond to further inquiries regarding Altair’s business. At the meeting, a representative of Siemens Industry indicated to Mr. Scapa that the managing board of Siemens AG would meet in early September to consider the potential acquisition of Altair by Siemens Industry.

On August 15, 2024, the Altair board of directors held a regularly scheduled meeting at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Members of Altair management presented an overview of (i) Altair’s business results and forecasts, (ii) Altair’s financial position, including cash outlook and projections and (iii) acquisition transactions. Representatives of

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Davis Polk and Lowenstein then reviewed with the Altair board of directors the fiduciary duties of the Altair board of directors in connection with its consideration of strategic alternatives. Following that, members of Altair management and representatives of Citi and J.P. Morgan provided an update to the Altair board of directors on the work undertaken in connection with the potential strategic transaction process, including the status of discussions with Siemens Industry and outreach to Party B, Party C, Party D and Party E. Representatives of Citi and J.P. Morgan advised the Altair board of directors why an acquisition of Altair would be challenging for financial sponsors as compared to potential strategic counterparties and identified additional potential strategic counterparties for the Altair board of directors to consider. After considering the current status of discussions with Siemens Industry, Party B, Party C, Party D and Party E, the Altair board of directors authorized Altair management, Citi and J.P. Morgan to reach out to additional strategic industry participants (referred to as “Party F” and “Party G”) and to formally engage with Party A if and when Altair management, Citi and J.P. Morgan determined such outreach was prudent, but otherwise instructed Altair management, Citi and J.P. Morgan to defer outreach to additional potential counterparties until the results of the current outreach to Siemens Industry, Party B, Party C, Party D and Party E became clearer.

On August 18, 2024, the Chair of the board of directors of Party D spoke telephonically with Mr. Scapa to discuss a potential strategic transaction between Altair and Party D. Later in the day, representatives of Citi and J.P. Morgan sent a form of non-disclosure agreement to Party D.

On August 19, 2024, after the initial outreach from representatives of Citi and J.P. Morgan, representatives of Party E spoke telephonically with Mr. Scapa to discuss Party E’s interest in pursuing discussions regarding a potential strategic transaction with Altair and receiving access to Altair’s confidential information to learn more about Altair’s business. Following that discussion, on August 20, 2024, representatives of Citi and J.P. Morgan sent a form of non-disclosure agreement to Party E.

On August 21, 2024, representatives of Citi and J.P. Morgan spoke telephonically with representatives of the financial advisor to Party B, during which call representatives of Citi and J.P. Morgan answered questions from representatives of the financial advisor to Party B and discussed next steps in the strategic process.

On August 26, 2024, Altair and Party B entered into a non-disclosure agreement to facilitate Altair’s provision of its confidential information to Party B in connection with a possible strategic transaction. The non-disclosure agreement included a customary standstill provision, which permitted Party B to make a confidential proposal or offer to the Altair board of directors with respect to a potential strategic transaction between Party B and Altair and which terminated, in accordance with its terms, upon Altair’s entry into the merger agreement.

On August 27, 2024, members of Altair management gave a presentation to representatives of Party B and its financial advisor concerning the business and prospects of Altair.

On August 29, 2024, Altair and Party E entered into a non-disclosure agreement to facilitate Altair’s provision of its confidential information to Party E in connection with a possible strategic transaction. The non-disclosure agreement included a customary standstill provision, which terminated, in accordance with its terms, upon Altair’s entry into the merger agreement.

On September 4, 2024, Party B advised representatives of Altair that Party B would not continue to consider a strategic transaction with Altair.

On September 7, 2024, at the instruction of Altair management and in accordance with the authorization provided by the Altair board of directors, representatives of Citi and J.P. Morgan conducted an outreach call with Party F.

On September 9, 2024, Party D advised representatives of Altair that Party D would not continue to consider a transaction with Altair, citing its own internal factors as driving its decision to not participate further in the process.

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On September 10, 2024, Siemens AG submitted a preliminary, non-binding written indication of interest for Siemens Industry to acquire 100% of Altair at $100.00 per share in cash (the “initial Siemens proposal”). The initial Siemens proposal included a draft exclusivity agreement that proposed an exclusivity period of 30 days and noted that Siemens AG would be able to promptly complete its diligence following receipt of access to diligence documentation. In addition, the initial Siemens proposal was subject to, among other conditions, receipt of acceptable voting agreements from certain beneficial owners of Altair common stock, no material adverse change in Altair’s business or financial position prior to execution of the merger agreement and approvals from antitrust, foreign investment and other regulatory authorities.

Also on September 10, 2024, Party F confirmed its interest in participating in the strategic process. Subsequently, representatives of Citi and J.P. Morgan sent a form of non-disclosure agreement to Party F.

On September 11, 2024, the Altair board of directors held a special meeting to discuss the status of the review of strategic alternatives, including the initial Siemens proposal, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Representatives of Citi and J.P. Morgan reviewed with the Altair board of directors the initial Siemens proposal and provided an update on the status of outreach to other parties, noting that they reached out to Party F, consistent with previous discussions, and recommended that the Altair board of directors consider efforts to reengage with Party A at this stage in the strategic review process. Representatives of Citi and J.P. Morgan then reviewed with the Altair board of directors certain preliminary financial information and data to assist the Altair board of directors in framing the initial Siemens proposal, including information regarding Altair’s trading performance and perspectives of certain equity research analysts (noting that certain equity research analysts viewed the trading price of Altair common stock as elevated due to the expectation of a strategic transaction involving Altair following the announcement of the acquisition of Ansys by Synopsys) and provided an overview of other recent industry acquisitions by strategic buyers. In addition, representatives of Citi and J.P. Morgan reviewed with the Altair board of directors certain levers that could enable Siemens AG to increase its offer price, including through the identification and quantification of synergies. Following discussions, the Altair board of directors concluded that the initial Siemens proposal did not adequately reflect the value of Altair and instructed Citi and J.P. Morgan to inform Siemens AG that it was not prepared to accept the $100.00 per share proposal as it undervalued Altair, with the message that the Altair board of directors would expect Siemens AG to submit a higher proposal if they were to consider further engagement with Siemens Industry and Siemens AG. The Altair board of directors authorized Altair management to continue engaging with Siemens Industry’s and Siemens AG’s due diligence inquiries to support an increased offer for Altair. Representatives of Citi and J.P. Morgan then reviewed with the Altair board of directors the potential benefits and detriments of expanding the list of strategic buyers invited to participate in the process. After careful consideration, taking into account the importance of confidentiality, the Altair board of directors directed Citi and J.P. Morgan to reach out to Party A, and reaffirmed its authorization of Altair management to contact Party G if Altair management determined such outreach was prudent based on the current status of the strategic review process, but determined not to contact any additional counterparties until Altair was able to better assess the likelihood that Party A, Party C, Party E, Party F and Party G would submit indications of interest.

Further on September 11, 2024, as directed by the Altair board of directors, representatives of J.P. Morgan and Citi conducted an outreach call with Party A.

On September 13, 2024, at the instruction of the Altair board of directors, representatives of Citi and J.P. Morgan informed representatives of Siemens AG that Altair was not prepared to accept the offer of $100.00 per share as it undervalued the company and that Siemens AG would need to submit a higher offer if the Altair board of directors was to consider further engagement with Siemens Industry and Siemens AG.

On September 16, 2024, Altair and Party F entered into a non-disclosure agreement to facilitate Altair’s provision of its confidential information to Party F in connection with a possible strategic transaction. The non-disclosure agreement included a customary standstill provision, which permitted Party F to make a private and confidential proposal to the Altair board of directors (or a committee thereof) with respect to a potential

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strategic transaction between Party F and Altair and which terminated, in accordance with its terms, upon Altair’s entry into the merger agreement.

Also on September 16, 2024, Party A advised representatives of Altair that Party A was not interested in pursuing a strategic transaction with Altair.

On September 17, 2024, members of Altair management presented an overview of Altair to members of Party F’s management.

On September 18, 2024, following the discussion with the Altair board of directors regarding companies that could potentially have an interest in a strategic transaction with Altair, Mr. Scapa reached out to Party G by email to discuss its interest in a potential strategic transaction with Altair. Party G subsequently advised Mr. Scapa that Party G was not interested in pursuing a strategic transaction with Altair.

On September 19, 2024, Party F advised representatives of Altair that Party F was not interested in pursuing a strategic transaction with Altair.

Also on September 19, 2024, representatives of Party C spoke telephonically with representatives of Citi and J.P. Morgan to indicate an interest in evaluating a potential strategic transaction involving Altair and Party C. Subsequently, representatives of Citi and J.P. Morgan sent a form of non-disclosure agreement to Party C.

Further on September 19, 2024, members of Altair management met with representatives of Siemens Industry and Siemens AG, attended by both parties’ financial advisors, in which Altair management discussed their views on certain future drivers of growth and management’s perspectives on Altair’s future financial performance.

Subsequently on September 19, 2024, the Altair board of directors held a special meeting to discuss the latest developments in the strategic review process and to review the unaudited financial projections prepared by or at the direction of Altair management, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Members of Altair management reviewed with the Altair board of directors certain unaudited financial forecasts prepared by or at the direction of Altair management (the “financial projections”) (see the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”), and described, among other things, the process for preparing the financial projections, including the methodology for extrapolation and underlying assumptions to the forecasted results. Representatives of Citi and J.P. Morgan then reported on the current status of discussions with potential bidders, including the following updates: (i) Party F had declined to proceed further; (ii) Party G had declined to participate, even before receiving any information or signing a non-disclosure agreement, indicating that the acquisition of Altair was not a strategic priority for Party G at the time; (iii) Party E remained in the process, though it was noted that it would be difficult for Party E to finance an all-cash transaction; and (iv) Party C was prepared to enter into a non-disclosure agreement.

On September 20, 2024, members of Altair management presented an overview of Altair to members of Party E management.

On September 22, 2024, the Altair board of directors held a special meeting to review the financial projections presented at the September 19, 2024 board meeting, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Members of Altair management noted that if approved, the financial projections would be provided to potential bidders. The Altair board of directors approved the financial projections as previously submitted on September 19, 2024 and authorized Citi and J.P. Morgan to use the financial projections for purposes of performing their financial analyses in connection with rendering their opinions to the Altair board of directors (as more fully described above under the sections titled “—Opinion of Citi” and “— Opinion of J.P. Morgan”), and authorized representatives of Citi and J.P. Morgan to provide the board-approved financial projections for the calendar years

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2024 through 2027 (referred to as Management Case 1 and Management Case 2, as defined in the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”) to interested bidders at the appropriate time.

On September 23, 2024, following the Altair board of directors’ approval thereof, representatives of Altair management provided Management Case 1 and Management Case 2 to Siemens Industry and Siemens AG.

On September 25, 2024, Altair and Party C entered into a non-disclosure agreement to facilitate Altair’s provision of its confidential information to Party C in connection with a possible strategic transaction. The non-disclosure agreement included a customary standstill provision, which permitted Party C to make a confidential proposal to the Chief Executive Officer of Altair or the Altair board of directors with respect to a potential strategic transaction between Party C and Altair and which terminated, in accordance with its terms, upon Altair’s entry into the merger agreement.

Also on September 25, 2024, members of Altair management presented an overview of Altair in person to members of Party C management.

On September 27, 2024, Siemens AG submitted a revised non-binding indication of interest to representatives of Altair, increasing its offer from $100.00 per share to $110.00 per share, in cash (the “second Siemens proposal”). Except for the increase in price, the second Siemens proposal was the same as the initial Siemens proposal, and, as with the initial Siemens proposal, Siemens Industry’s and Siemens AG’s willingness to proceed was predicated on Altair entering into exclusivity with Siemens AG. Siemens AG stated its desire to reach a definitive agreement by October 30, 2024.

On October 1, 2024, a representative of Party C spoke telephonically with a representative of Citi to indicate that Party C was continuing to evaluate and discuss internally the potential for a strategic transaction involving Altair and Party C, but noted that, while a majority of Altair’s business would be a highly attractive asset to Party C, other portions of Altair’s business were perceived to be less of a strategic fit for Party C. As a result, the valuation that Party C believed would be required to transact with Altair would be more significant when measured against the most strategic portion of Altair’s business. The representative of Party C also conveyed that no additional information was required from Altair to continue its review.

On October 2, 2024, the Altair board of directors held a special meeting to discuss the status of the strategic review process and to discuss the second Siemens proposal, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Representatives of Davis Polk provided an overview of the directors’ fiduciary duties in the context of evaluating strategic alternatives, including a potential sale of Altair. Representatives of Citi and J.P. Morgan provided an update to the Altair board of directors regarding the status of discussions with potential counterparties to a strategic transaction with Altair. At this time, the parties that remained in the process were Siemens AG, Party C and Party E. Representatives of Citi and J.P. Morgan shared their perspective that there was a low likelihood that either Party C or Party E would submit a competitive bid. The Altair board of directors discussed with representatives of Citi and J.P. Morgan the second Siemens proposal and the range of options for responding. Representatives of Citi and J.P. Morgan then presented certain preliminary financial information and data regarding Altair and the second Siemens proposal, based on the board-approved financial projections. Following discussions, the Altair board of directors concluded that the second Siemens proposal continued to undervalue Altair and authorized Citi and J.P. Morgan to convey to Siemens AG that the increased proposal remained insufficient, did not recognize the full value of Altair’s business, and to seek an additional increase in Siemens AG’s bid price and to continue responding to Siemens Industry’s and Siemens AG’s due diligence inquiries in the meantime.

On October 3, 2024, as instructed by the Altair board of directors, representatives of J.P. Morgan and Citi spoke with representatives of Siemens AG and delivered feedback from the Altair board of directors that the offer price of $110.00 per share was not acceptable and encouraged Siemens AG to submit a higher proposal.

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On October 8, 2024, representatives of Siemens AG informed representatives of Altair that Siemens AG was prepared to increase its bid to $113.00 per share, in cash (the “third Siemens proposal”) and advised representatives of Altair that its offer was conditioned on receiving exclusivity through November 10, 2024. Representatives of Siemens AG also indicated this was Siemens AG’s “best and final” proposal.

Subsequently on October 8, 2024, the Altair board of directors held a special meeting to discuss the third Siemens proposal, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Representatives of Citi and J.P. Morgan presented certain preliminary financial information and data regarding the third Siemens proposal, and then updated the Altair board of directors on the status of the other potential bidders. It was noted that Party C had not engaged with Altair or its advisors since its meeting with Altair management on September 25, 2024 and the call with a representative of Citi on October 1, 2024. Based on the very limited engagement demonstrated by Party C and the concerns raised by Party C during its call with a representative of Citi on October 1, 2024, the Altair board of directors determined that there was a very low likelihood that Party C would submit a proposal. The Altair board of directors discussed the fact that granting exclusivity to Siemens AG would prevent Altair from engaging with other interested parties but noted that Altair had reached out to all strategic acquirors who would most likely be able to submit a compelling offer, and no such counterparty had submitted a proposal for a strategic transaction or indicated an intent to do so. In light of the foregoing, the Altair board of directors determined that it was in the best interests of Altair and its stockholders to grant Siemens AG a limited period of exclusivity. Following discussions, the Altair board of directors authorized Citi and J.P. Morgan to inform Siemens AG that Altair was prepared to proceed with negotiations along the lines set forth in the initial Siemens proposal, subject to a price of $113.00 per share and an exclusivity period that would extend until November 10, 2024. Further, the Altair board of directors authorized Davis Polk and Lowenstein (in each case, on behalf of Mr. Scapa) to prepare and negotiate the terms of a voting agreement with Siemens Industry and further authorized Davis Polk and Lowenstein to prepare and negotiate the merger agreement and the other transaction documents contemplated by the third Siemens proposal. Following conclusion of the board meeting on October 8, 2024, representatives of Citi and J.P. Morgan communicated the Altair board of directors’ message to representatives of Siemens AG.

Further on October 8, 2024, Party E advised representatives of J.P. Morgan that Party E would not continue to consider a strategic transaction with Altair.

On October 9, 2024, Altair and Siemens AG executed an exclusivity agreement that prohibited Altair from negotiating with any potential bidder other than Siemens AG through November 10, 2024.

Also on October 9, 2024, representatives of J.P. Morgan shared an initial draft of the clean team agreement from Davis Polk, providing for restrictions relating to the review of certain competitively sensitive information, with Siemens AG’s counsel, Latham & Watkins LLP (“Latham”). Subsequently on October 9, 2024, Latham sent a revised draft of the clean team agreement to Davis Polk.

On October 10, 2024, Altair and Siemens AG executed the clean team agreement.

Between October 10, 2024 and October 22, 2024, representatives of Altair, Siemens Industry and Siemens AG held a number of virtual and in-person meetings, with each party’s legal and financial advisors in attendance for certain meetings, in which Altair management discussed certain diligence topics and answered other diligence questions from Siemens Industry and Siemens AG.

On October 11, 2024, representatives of Citi provided representatives of Siemens Industry, Siemens AG and Latham with access to a virtual data room.

On October 13, 2024, representatives of Davis Polk provided the Altair board of directors with a draft and a summary of the proposed merger agreement that Davis Polk had prepared (the “initial draft merger agreement”)

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and information regarding the purpose and potential scope of the voting support agreement requested by Siemens AG in the initial Siemens proposal.

On October 14, 2024, Davis Polk shared the initial draft merger agreement with Latham.

On October 17, 2024, Latham sent Davis Polk and Lowenstein a markup to the initial draft merger agreement.

On October 18, 2024, Davis Polk sent Latham an initial draft of the disclosure schedules to the merger agreement. Davis Polk, on behalf of Mr. Scapa, also sent Latham an initial draft of the voting agreement, which contemplated Mr. Scapa and certain entities and trusts affiliated with Mr. Scapa (i) voting their shares of Altair common stock in favor of the adoption of the merger agreement at the meeting of Altair stockholders, (ii) not transferring their shares of Altair common stock, subject to certain limited exceptions, and (iii) complying with certain non-solicitation obligations.

On October 20, 2024, the Altair board of directors held a special meeting to discuss the strategic review process, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Representatives of Citi and J.P. Morgan noted that only Siemens AG was continuing to engage in the process following Party E’s decision not to proceed and provided an update on the status of negotiations with Siemens AG. Representatives of Citi and J.P. Morgan then exited the meeting. Representatives of Davis Polk reviewed with the Altair board of directors certain key points presented by the markup to Altair’s draft merger agreement sent by Latham, including, among other things: (i) the identity of the counterparty to the merger agreement being Siemens Industry, a subsidiary of Siemens AG, (ii) the efforts required to obtain regulatory approvals, which Siemens AG proposed should be a reasonable best efforts standard rather than a hell or high water standard, (iii) a termination fee equal to 4% of equity value to be paid by Altair to Siemens Industry upon a termination of the merger agreement in certain circumstances, and (iv) certain edits to the proposed closing conditions. Following discussions, the Altair board of directors provided feedback on the terms of the merger agreement and instructed representatives of Davis Polk to (i) convey to Latham that Altair would consider Siemens AG’s proposed regulatory efforts standard only if Siemens AG agreed to a reverse termination fee equal to 7% of equity value, (ii) negotiate for a termination fee to be paid by Altair if the merger agreement was terminated under certain circumstances equal to 3% of equity value and (iii) narrow the closing conditions.

Following the board meeting on October 20, 2024, Davis Polk, Lowenstein and Latham had a virtual meeting to discuss key outstanding points in the merger agreement. As instructed by the Altair board of directors, Davis Polk and Lowenstein conveyed the Altair board of director’s feedback on the merger agreement, and proposed a reverse termination fee equal to 7% of equity value and a termination fee equal to 3% of equity value. Over the next several days, Davis Polk, Lowenstein and Latham continued to negotiate the terms of the merger agreement.

Also on October 20, 2024, Latham sent Davis Polk and Lowenstein (i) an initial draft of the deed of guarantee, under which Siemens AG would guarantee certain obligations of Siemens Industry under the merger agreement, and (ii) a revised draft of the voting agreement.

On October 21, 2024, (i) Davis Polk sent Latham a revised draft of the merger agreement, reflecting the terms of their discussion the previous day, and (ii) Davis Polk, on behalf of Mr. Scapa, sent Latham a revised draft of the voting agreement. Also on October 21, 2024, Latham sent Davis Polk and Lowenstein a revised draft of the disclosure schedules.

On October 22, 2024, Reuters published an article indicating that Altair was exploring strategic alternatives with respect to a potential sale after receiving acquisition interest. The trading price of Altair common stock increased by approximately 8% on that day. Neither Altair nor Siemens AG commented on the Reuters article.

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Also on October 22, 2024, Latham sent Davis Polk and Lowenstein a revised draft of the merger agreement and Davis Polk sent Latham revised drafts of the deed of guarantee and disclosure schedules.

On October 23, 2024, Bloomberg published an article identifying Siemens AG as a potential acquiror. The trading price of Altair common stock increased by approximately 4% on that day. Neither Altair nor Siemens AG commented on the Bloomberg article.

Also on October 23, 2024, Davis Polk, Lowenstein and Latham had a virtual meeting to discuss key outstanding issues in the merger agreement.

On October 24, 2024, Davis Polk sent a revised draft of the merger agreement to Latham, reflecting the discussion on the previous day, including a proposed reverse termination fee equal to 6.5% of equity value to be paid by Siemens Industry to Altair in the event the merger was terminated under certain circumstances and tightened closing conditions, but did not make a counterproposal for the termination fee to be paid by Altair if the merger agreement was terminated under certain circumstances, consistent with prior discussions with the Altair board of directors. Also on October 24, 2024, Latham sent Davis Polk and Lowenstein a revised draft of the disclosure schedules.

On October 25, 2024, Latham sent a revised draft of the merger agreement to Davis Polk and Lowenstein, reflecting a proposed reverse termination fee payable by Siemens Industry equal to 6% of equity value and a proposed termination fee payable by Altair equal to 3.5% of equity value. Also on October 25, 2024, Latham sent revised drafts of the voting agreement and deed of guarantee to Davis Polk and Lowenstein. Further, Latham provided Davis Polk and Lowenstein with an initial draft of a restrictive covenant agreement to be entered into by Mr. Scapa, which would restrict Mr. Scapa’s ability to (i) solicit employees, (ii) participate in the operations of certain entities competing with Siemens Industry and (iii) disclose Altair’s confidential information. Also on October 25, 2024, Davis Polk sent Latham a revised draft of the disclosure schedules.

From October 26, 2024 through October 30, 2024, Davis Polk, Lowenstein and Latham exchanged revised drafts of the merger agreement and the other transaction documents and continued to negotiate the terms of such documents.

On October 27, 2024, the Altair board of directors held a special meeting to discuss the status of negotiations with Siemens AG, at which members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Prior to the meeting, current drafts of the merger agreement, voting agreement and deed of guarantee had been circulated to the Altair board of directors. Representatives of Citi and J.P. Morgan discussed news of the leak on October 22, 2024, and the impact of the leak. Representatives of Citi and J.P. Morgan then presented preliminary financial analyses of the third Siemens proposal and regarding Altair based on the financial projections. Representatives of Davis Polk reviewed with the Altair board of directors their fiduciary duties in connection with the strategic review process, as well as the key terms of the merger agreement, voting agreement, deed of guarantee and restrictive covenant agreement, and updated the Altair board of directors as to the status of outstanding issues in the transaction documents.

On October 30, 2024, the Altair board of directors held a special meeting to vote on the proposed merger agreement and other related agreements and matters, at which meeting members of Altair management and representatives of Citi, J.P. Morgan, Davis Polk and Lowenstein were also present. Prior to the meeting, copies of the execution versions of the merger agreement (including the disclosure schedules and the exhibits thereto), voting agreement and deed of guarantee were provided to the Altair board of directors. At the meeting, representatives of Davis Polk reviewed with the Altair board of directors its fiduciary duties in considering the proposed transaction, as well as the terms of the proposed final merger agreement and other transaction documents, and updated the Altair board of directors as to the resolution of key issues in such agreements. Counsel also reviewed with the Altair board of directors certain matters as to which the interests of Altair’s officers and directors may be different than the interests of Altair’s stockholders. Representatives of Citi and J.P.

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Morgan then each reviewed a financial analysis of the merger consideration and, at the request of the Altair board of directors, rendered oral opinions, confirmed by delivery of written opinions dated October 30, 2024, to the Altair board of directors to the effect that, as of that date and based on and subject to various assumptions made, procedures followed, matters considered and limitations and qualifications described in the opinions, the merger consideration to be received by holders of Altair common stock in the merger pursuant to the merger agreement was fair, from a financial point of view, to such holders. Representatives of Citi and J.P. Morgan then exited the meeting. The Altair board of directors then unanimously (i) determined that the merger agreement, the other transaction documents and the proposed transaction, on the terms and subject to the conditions set forth in the merger agreement, were fair to and in the best interests of Altair and its stockholders, (ii) declared that the merger agreement, the other transaction documents and the proposed transaction were advisable, (iii) approved the merger agreement and the other transaction documents, the execution and delivery by Altair of the merger agreement and the other transaction documents and the performance by Altair of the agreements contained in the merger agreement and the consummation of the proposed transaction, on the terms and subject to the conditions contained in the merger agreement; (iv) directed that the adoption of the merger agreement be submitted to a vote at a meeting of Altair stockholders and (v) resolved to recommend adoption of the merger agreement and the proposed transaction to the stockholders of Altair.

Shortly after the market closed on October 30, 2024, the merger agreement was executed and delivered, the disclosure schedules were provided in final form and the voting agreement, deed of guarantee and restrictive covenant agreement were executed and delivered. Promptly thereafter, Altair and Siemens AG each separately issued press releases to announce the proposed transaction.

Altair’s Reasons for the Merger; Recommendation of Altair’s Board of Directors

At its October 30, 2024 meeting held to evaluate the merger, the Altair board of directors unanimously (i) determined the merger agreement, the other transaction documents and the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions set forth in the merger agreement, to be fair to and in the best interests of Altair and its stockholders, (ii) declared that the merger agreement, the other transaction documents and the transactions contemplated by the merger agreement, including the merger, advisable, (iii) approved the merger agreement and the other transaction documents, the execution and delivery by Altair of the merger agreement and the other transaction documents, the performance by Altair of the agreements contained in the merger agreement and the consummation of the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions contained in the merger agreement, (iv) directed that the adoption of the merger agreement be submitted to a vote at a meeting of Altair stockholders and (v) resolved to recommend adoption of the merger agreement and the transactions contemplated by the merger agreement, including the merger, to Altair stockholders. The Altair board of directors recommends that Altair stockholders vote:

In evaluating the merger agreement and merger and arriving at its determination, the Altair board of directors consulted with Altair’s senior management, representatives of Altair’s financial advisors, Citi and J.P. Morgan, and Altair’s outside legal counsel, Davis Polk and Lowenstein, and considered a number of substantive factors, both positive and negative, and potential benefits and detriments of the merger to Altair and Altair stockholders. The Altair board of directors believed that, taken as a whole, the following factors (which are not presented in any relative order of importance) supported its decision to approve the merger:

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The Altair board of directors also considered certain potentially negative factors in its deliberations concerning the merger, including the following (which are not presented in any relative order of importance):

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The Altair board of directors concluded that the potentially negative factors associated with the merger were significantly outweighed by the potential benefits that it expected Altair stockholders would achieve as a result of the merger. The Altair board of directors believed that the merger would maximize the immediate value of the shares held by Altair stockholders and minimize the risks and uncertainty affecting the future prospects of Altair, including the potential execution risks associated with its standalone financial plan. Accordingly, the Altair board of directors unanimously (i) determined the merger agreement, the other transaction documents and the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions set forth in the merger agreement, to be fair to and in the best interests of Altair and its stockholders, (ii) declared that the merger agreement, the other transaction documents and the transactions contemplated by the merger agreement, including the merger, advisable, (iii) approved the merger agreement and the other transaction documents, the execution and delivery by Altair of the merger agreement and the other transaction documents, the performance by Altair of the agreements contained in the merger agreement and the consummation of the transactions contemplated by the merger agreement, including the merger, on the terms and subject to the conditions contained in the merger agreement, (iv) directed that the adoption of the merger agreement be submitted to a vote at a meeting of Altair stockholders and (v) resolved to recommend adoption of the merger agreement and the transactions contemplated by the merger agreement, including the merger, to Altair stockholders.

In addition, the Altair board of directors was aware of and considered the interests that Altair’s directors and executive officers may have with respect to the merger that differ from, or are in addition to, the interests of Altair stockholders generally, as described below under “—Interests of Altair’s Directors and Executive Officers in the Merger.”

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The foregoing discussion of the information and factors considered by the Altair board of directors is not exhaustive, but Altair believes it includes all the material factors considered by the Altair board of directors. In view of the wide variety of factors considered in connection with its evaluation of the merger and the complexity of these matters, the Altair board of directors did not consider it practicable to, and did not attempt to, quantify or otherwise assign relative or specific weight or values to any of these factors. Rather, the Altair board of directors viewed its position and recommendation as being based on an overall analysis and on the totality of the information presented to and factors considered by it. In addition, in considering the factors described above, individual directors may have given different weights to different factors. The Altair board of directors based its unanimous recommendation on the totality of the information presented.

This explanation of Altair’s reasons for the merger and other information presented in this section is forward-looking in nature and, therefore, should be read in light of the factors described under “Cautionary Statement Regarding Forward-Looking Statements.”

Opinion of Citi

Pursuant to an engagement letter dated August 7, 2024, Altair engaged Citi as its co-financial advisor in connection with the merger. On October 30, 2024, Citi rendered its oral opinion to the Altair board of directors (which was subsequently confirmed in writing by delivery of Citi’s written opinion addressed to the Altair board of directors dated the same date) as to, as of October 30, 2024, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by Citi as set forth in its written opinion, the fairness, from a financial point of view, to the holders of Altair common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement.

The full text of Citi’s written opinion, which describes, among other things, the assumptions made, procedures followed, matters considered and qualifications and limitations on the review undertaken, is attached as Annex D to this proxy statement, and is incorporated by reference into this proxy statement. The description of Citi’s opinion contained in this proxy statement is qualified in its entirety by reference to the full text of the opinion. Citi’s opinion, the issuance of which was approved by Citi’s fairness opinion committee, was directed to the Altair board of directors, in its capacity as such, and addressed only the fairness, from a financial point of view and as of the date of such opinion, to the holders of Altair common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement. Citi’s opinion did not address any other terms, aspects or implications of the merger. Citi expressed no view as to, and its opinion did not address, the underlying business decision of Altair to effect or enter into the merger, the relative merits of the merger as compared to any alternative business strategies that might exist for Altair or the effect of any other transaction in which Altair might engage or consider. Citi’s opinion is not intended to be and does not constitute a recommendation as to how the Altair board of directors or any Altair stockholder should vote or act on any matters relating to the merger or otherwise.

In arriving at its opinion, Citi, among other things:

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In rendering its opinion, Citi assumed and relied, without independent verification, upon the accuracy and completeness of all financial and other information and data publicly available or provided to or otherwise reviewed by or discussed with Citi and upon the assurances of Altair management that they were not aware of any relevant information that had been omitted or that remained undisclosed to Citi. With respect to financial forecasts and other information and data relating to Altair provided to or otherwise reviewed by or discussed with Citi, Citi had been advised by Altair management that such forecasts and other information and data were reasonably prepared on bases reflecting the best currently available estimates and judgments of Altair management as to the future financial performance of Altair and the other matters addressed thereby. Citi expressed no view or opinion as to any financial forecasts and other information or data (or underlying assumptions on which any such financial forecasts and other information or data were based) provided to or otherwise reviewed by or discussed with Citi and Citi assumed, at Altair’s direction, that such financial forecasts and other information or data represented a reasonable basis upon which to evaluate Altair and the merger.

Citi assumed, with Altair’s consent, that the merger would be consummated in accordance with its terms, without waiver, modification or amendment of any material term, condition or agreement and that, in the course of obtaining the necessary regulatory or third-party approvals, consents and releases for the merger, no delay, limitation, restriction or condition would be imposed that would have an adverse effect on Altair or the merger or that otherwise would be meaningful in any respect to Citi’s analyses or opinion. Representatives of Altair had advised Citi, and Citi further assumed, that the final terms of the merger agreement would not vary materially from those set forth in the draft reviewed by Citi.

Citi did not express any view or opinion with respect to accounting, tax, regulatory, legal or similar matters, including, without limitation, as to tax or other consequences of the merger or otherwise or changes in, or the impact of, accounting standards or tax and other laws, regulations and governmental and legislative policies affecting Altair, and Citi relied, with Altair’s consent, upon the assessments of representatives of Altair as to such matters. Citi had not made or been provided with an independent evaluation or appraisal of the assets or liabilities (contingent or otherwise) of Altair, nor had Citi made any physical inspection of the properties or assets of Altair. Citi did not evaluate the solvency or fair value of Altair, Siemens Industry or any other entity under any state, federal or other laws relating to bankruptcy, insolvency or similar matters. Citi expressed no view or opinion as to the potential impact on Altair or any other entity of any actual or potential litigation, claims or governmental, regulatory or other proceedings, enforcement actions or consent or other orders or investigations.

Citi’s opinion addressed only the fairness, from a financial point of view and as of the date thereof, to the holders of Altair common stock of the merger consideration (to the extent expressly specified therein), without regard to individual circumstances of specific holders (whether by virtue of control, voting, liquidity, contractual

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arrangements or otherwise) which may distinguish such holders. Citi’s opinion did not address any other terms, aspects or implications of the merger, including, without limitation, the form or structure of the merger or any terms, aspects or implications of any other agreement, arrangement or understanding to be entered into in connection with or contemplated by the merger or otherwise (including any voting agreement). Citi was advised that the certificate of incorporation of Altair, as in effect on the date of its opinion, contemplates (except in accordance with procedures specified therein) that the shares of Class A common stock and the shares of Class B common stock are to be treated identically with respect to the merger consideration to be received in the merger, and accordingly, at Altair’s direction, for purposes of its analyses and opinion, Citi treated the shares of Class A common stock and the shares of Class B common stock as identical. Citi expressed no opinion as to the allocation of the aggregate merger consideration to be paid to all holders of Altair common stock between the holders of Class A common stock and the holders of Class B common stock that results from the merger pursuant to the terms of the merger agreement, or the relative fairness of the merger consideration to the holders of any shares of Altair common stock.

Citi expressed no view as to, and Citi’s opinion did not address, the underlying business decision of Altair to effect or enter into the merger, the relative merits of the merger as compared to any alternative business strategies that might exist for Altair or the effect of any other transaction which Altair might engage in or consider. Citi expressed no view as to, and Citi’s opinion does not address, the fairness (financial or otherwise) of the amount or nature or any other aspect of any compensation or other consideration to any officers, directors or employees of any parties to the merger (in their capacity as such), or any class of such persons, relative to the merger consideration or otherwise. Citi’s opinion is necessarily based upon information available to Citi, and financial, stock market and other conditions and circumstances existing, as of the date of its opinion. Although developments occurring or coming to Citi’s attention after the date of its opinion may affect Citi’s opinion, Citi has no obligation to update, revise or reaffirm its opinion.

In preparing its opinion, Citi performed a variety of financial and comparative analyses, including those described below. The summary of the analyses below is not a complete description of Citi’s opinion or the analyses underlying, and factors considered in connection with, Citi’s opinion. The preparation of a financial opinion is a complex analytical process involving various determinations as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances and, therefore, a financial opinion is not readily susceptible to summary description. Citi arrived at its ultimate opinion based on the results of all analyses and factors assessed as a whole, and it did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis. Accordingly, Citi believes that the analyses must be considered as a whole and in context and that selecting portions of its analyses and factors or focusing on information presented in tabular format, without considering all analyses and factors or the narrative description of the analyses, could create a misleading or incomplete view of the processes underlying such analyses and its opinion.

In its analyses, Citi considered business, economic, industry and market conditions, financial and otherwise, and other matters as they existed on, and could be evaluated as of, the date of its opinion. No company, business or transaction used in Citi’s analyses for comparative purposes is identical to Altair or the merger. While the results of each analysis were taken into account in reaching its overall conclusion with respect to the fairness, from a financial point of view, of the merger consideration (to the extent expressly specified in Citi’s opinion), Citi did not make separate or quantifiable judgments regarding individual analyses. The reference ranges indicated by Citi’s financial analyses are illustrative and not necessarily indicative of actual values nor predictive of future results or values, which may be significantly more or less favorable than those suggested by the analyses. In addition, any analyses relating to the value of assets, businesses or securities do not purport to be appraisals or to reflect the prices at which businesses or securities actually may be sold, which may depend on a variety of factors, many of which are beyond Altair’s control and the control of Citi. Much of the information used in, and accordingly the results of, Citi’s analyses are inherently subject to substantial uncertainty.

Citi was selected by Altair to act as its co-financial advisor based on Citi’s qualifications, experience and reputation. Citi was not requested to, and it did not, recommend or determine the specific consideration payable

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in the merger or opine that any specific consideration constituted the only appropriate consideration for the merger. The type and amount of consideration payable in the merger were determined through arm’s-length negotiations between Altair and Siemens Industry and the decision of Altair to enter into the merger agreement was solely that of the Altair board of directors.

Citi’s opinion to the Altair board of directors was one of many factors taken into consideration by the Altair board of directors in evaluating the merger. Consequently, the analyses described above should not be viewed as determinative of the opinion of the Altair board of directors with respect to the merger consideration or of whether the Altair board of directors or management would have been willing to agree to a different merger consideration. The issuance of Citi’s opinion was authorized by Citi’s fairness opinion committee.

Summary of Financial Analyses of Citi

The following is a summary of the material financial analyses performed by Citi in connection with its oral opinion and the preparation of its written opinion to the Altair board of directors, both provided as of October 30, 2024. The following summary is not a complete description of the financial analyses performed and factors considered by Citi in connection with its opinion, nor does the order of analyses described represent the relative importance or weight given to those analyses. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed before October 30, 2024. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by Citi, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The analyses listed in the tables and described below must be considered as a whole. Assessing any portion of such analyses and of the factors reviewed, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Citi’s opinion. Furthermore, mathematical analysis is not in itself a meaningful method of using the data referred to below.

For purposes of its financial analyses and opinion, Citi compared ranges of values indicated by its analyses with the per share merger consideration of $113.00. For its analyses, Citi utilized and relied upon the number of issued and outstanding shares of Altair provided by Altair management.

Selected Public Companies Analysis

Citi performed a selected public companies analysis of Altair for which Citi reviewed certain financial and stock market information relating to Altair and the selected publicly traded companies listed below that are engaged in the engineering software business and which Citi deemed comparable to Altair in one or more respects.

For the selected companies noted below, Citi considered, among other things, the ratio of enterprise value (defined as market capitalization plus net debt, preferred equity and minority interests) (“enterprise value”) to calendar year 2025 estimated unlevered free cash flow (or “UFCF”) based on research consensus estimates. For purposes of Citi’s analysis, in deriving ranges of implied values for Altair, Citi used the estimates reflected in Management Case 1 and Management Case 2 for the applicable financial data of Altair.

The selected companies considered by Citi for its analysis of Altair were:

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Citi noted that, based on market data as of October 29, 2024 (or, in the case of Ansys, December 21, 2023, representing the last unaffected trading day of Ansys common stock prior to published rumors of public takeover interest in Ansys), the low, high and median enterprise value to estimated calendar year 2025 UFCF multiples for the selected companies was 25.7x, 48.9x and 32.1x, respectively. Based upon the application of its professional judgment and experience, Citi applied the multiple range of 30.0x to 50.0x to Altair’s estimated calendar year 2025 UFCF (based on Management Case 1 and Management Case 2). This analysis indicated an approximate implied per share equity value reference range for Altair of $55.75 to $88.45 (Management Case 1) and $57.50 to $91.15 (Management Case 2), as compared to the per share merger consideration in the merger of $113.00.

Selected Precedent Transactions Analysis

Citi performed a selected precedent transactions analysis of Altair, which is designed to derive an implied value of a company based on publicly available financial terms for selected transactions. In connection with its analysis, Citi reviewed publicly available financial data for certain transactions involving targets Citi deemed comparable in one or more respects since 2020.

The selected transactions considered by Citi for its analysis of Altair were:

The financial data reviewed by Citi included the enterprise value of the target company implied by the consideration payable by the acquiror in the selected transaction as a multiple of estimated UFCF for the twelve months following the announcement of the transaction (“NTM UFCF”). Citi noted that the low, high, mean and median transaction value to NTM UFCF multiples for the selected transactions were 38.4x, 60.8x, 48.0x and 47.4x, respectively. Based on the application of its professional judgment and experience, Citi applied the multiple range of 50.0x to 60.0x to Altair’s estimated NTM UFCF (based on Management Case 1 and Management Case 2). This analysis indicated an approximate implied per share equity value reference range for Altair of $84.25 to $99.30 (Management Case 1) and $86.25 to $101.75 (Management Case 2), as compared to the per share merger consideration in the merger of $113.00.

Discounted Cash Flow Analysis

Citi performed a discounted cash flow analysis for Altair by calculating the estimated present value (as of September 30, 2024) of the standalone UFCFs (calculated for purposes of the discounted cash flow analysis after giving effect to estimates of stock-based compensation provided by Altair management, “Post-SBC UFCF”) that Altair was forecasted to generate during the fourth quarter of 2024 and the calendar years ending December 31, 2025 through December 31, 2034 based on Management Case 1 and the related extrapolations therefrom reviewed and approved by the Altair board of directors and Management Case 2 and the related extrapolations therefrom reviewed and approved by the Altair board of directors (in each case, as further described in the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”). Based on its judgment and experience, Citi applied a perpetuity growth rate of 6.0% to 8.0% to Altair’s estimated terminal year Post-SBC UFCF. The present values (as of September 30, 2024) of the cash flows and implied terminal values were then calculated using a selected range of discount rates of 11.9% to 12.9%, which were selected based on Citi’s judgment and experience. This analysis indicated an approximate implied per share equity value reference range for Altair of $48.65 to $76.15 (Management Case 1 and the related extrapolations therefrom) and $53.80 to $84.05 (Management Case 2 and the related extrapolations therefrom), as compared to the per share merger consideration in the merger of $113.00.

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Certain Additional Information

Citi also observed certain additional information that was not considered part of its financial analyses with respect to its opinion but was noted for informational purposes, including the following:

Historical Trading Prices

Citi reviewed the historical trading range of Class A common stock for the 52-week period through October 21, 2024 (the last trading day before published market rumors of a potential acquisition of Altair). Citi noted that the low and high closing prices for the Class A common stock were as follows:

Equity Research

Citi reviewed sell-side analyst price targets for shares of Class A common stock published by eight equity research analysts during the time period from September 10, 2024 through October 22, 2024. These targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of Class A common stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of Class A common stock was $71.00 per share to $105.00 per share. To facilitate a comparison with the merger consideration, Citi discounted the price target range to present value by applying, for a one-year discount period, an illustrative discount rate of 12.8%, which was selected by Citi based on Altair’s assumed cost of equity. The resulting discount indicated a range of discounted price targets for shares of Class A common stock of $62.95 per share to $93.10 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of Class A common stock and these estimates are subject to uncertainties, including the future financial performance of Altair and future financial market conditions.

Miscellaneous

Citigroup Global Markets Inc. has acted as co-financial advisor to Altair in connection with the merger and will receive a fee currently estimated to be approximately $63.8 million for such services, of which $5.0 million became payable in connection with the delivery of the opinion and has been paid, and the remainder is payable upon the consummation of the merger. Altair has agreed to reimburse Citi for its expenses, including fees and expenses of counsel, incurred in connection with its engagement. In addition, Altair has agreed to indemnify Citi and related parties against certain liabilities, including liabilities under the federal securities laws, relating to or arising out of Citi’s engagement.

Citi and its affiliates in the past have provided, and currently provide, services to Siemens Industry and its affiliates, unrelated to the merger, for which services Citi and its affiliates have received compensation, including, without limitation, during the two-year period prior to delivery of its opinion, having acted, and continuing to act, as a lender to affiliates of Siemens Industry (for which Citi and its affiliates received during such period fees, in the aggregate, of less than $1 million). In the ordinary course of its business, Citi and its affiliates may actively trade or hold the securities of Altair and affiliates of Siemens Industry for its own account or for the account of its customers and, accordingly, may at any time hold a long or short position in such securities. In addition, Citi and its affiliates (including Citigroup Inc. and its affiliates) may maintain relationships with Altair, Siemens Industry and their respective affiliates.

Opinion of J.P. Morgan

Pursuant to an engagement letter dated August 2, 2024, Altair retained J.P. Morgan as its co-financial advisor in connection with the merger and to deliver a fairness opinion in connection with the merger.

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At the meeting of the Altair board of directors on October 30, 2024, representatives of J.P. Morgan rendered its oral opinion to the Altair board of directors that, as of such date and based upon and subject to the factors and assumptions set forth in its written opinion, the merger consideration to be paid to the holders of Altair common stock in the merger was fair, from a financial point of view, to such holders. J.P. Morgan confirmed its October 30, 2024 oral opinion by delivering its written opinion to the Altair board of directors, dated October 30, 2024, that, as of such date, the merger consideration to be paid to the holders of Altair common stock in the merger was fair, from a financial point of view, to such holders.

The full text of the written opinion of J.P. Morgan, dated October 30, 2024, which sets forth, among other things, the assumptions made, matters considered and limits on the review undertaken, is attached as Annex E to this proxy statement and is incorporated herein by reference. The summary of the opinion of J.P. Morgan set forth in this proxy statement is qualified in its entirety by reference to the full text of such opinion. Altair stockholders are urged to read the opinion in its entirety. J.P. Morgan’s opinion was addressed to the Altair board of directors (in its capacity as such) in connection with and for the purposes of its evaluation of the merger, was directed only to the merger consideration to be paid to the holders of Altair common stock in the merger and did not address any other aspect of the merger. J.P. Morgan expressed no opinion as to the fairness of the merger consideration to the holders of any other class of securities, creditors or other constituencies of Altair or as to the underlying decision by Altair to engage in the merger. The issuance of J.P. Morgan’s opinion was approved by a fairness committee of J.P. Morgan. The opinion does not constitute a recommendation to any stockholder of Altair as to how such stockholder should vote with respect to the merger or any other matter.

In arriving at its opinion, J.P. Morgan, among other things:

In addition, J.P. Morgan held discussions with certain members of Altair management with respect to certain aspects of the merger, and the past and current business operations of Altair, the financial condition and future prospects and operations of Altair, and certain other matters J.P. Morgan believed necessary or appropriate to its inquiry.

In giving its opinion, J.P. Morgan relied upon and assumed the accuracy and completeness of all information that was publicly available or was furnished to or discussed with J.P. Morgan by Altair and Siemens Industry or otherwise reviewed by or for J.P. Morgan. J.P. Morgan did not independently verify any such information or its accuracy or completeness and, pursuant to its engagement letter with Altair, did not assume any obligation to undertake any such independent verification. J.P. Morgan did not conduct and was not provided

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with any valuation or appraisal of any assets or liabilities, nor did J.P. Morgan evaluate the solvency of Altair or Siemens Industry under any state or federal laws relating to bankruptcy, insolvency or similar matters. In relying on financial analyses and forecasts provided to J.P. Morgan or derived therefrom, J.P. Morgan assumed that they were reasonably prepared based on assumptions reflecting the best currently available estimates and judgments by management of Altair as to the expected future results of operations and financial condition of Altair to which such analyses or forecasts relate. J.P. Morgan expressed no view as to such analyses or forecasts or the assumptions on which they were based. J.P. Morgan assumed that the merger and the other transactions contemplated by the merger agreement will be consummated as described in the merger agreement, and that the definitive merger agreement would not differ in any material respects from the draft thereof furnished to J.P. Morgan. J.P. Morgan also assumed that the representations and warranties made by Altair and Siemens Industry in the merger agreement and the related agreements were and will be true and correct in all respects material to its analysis. J.P. Morgan is not a legal, regulatory or tax expert and relied on the assessments made by advisors to Altair with respect to such issues. J.P. Morgan further assumed that all material governmental, regulatory or other consents and approvals necessary for the consummation of the merger will be obtained without any adverse effect on Altair or on the contemplated benefits of the merger.

The unaudited financial projections for calendar years 2024 through 2027 (referred to as Management Case 1 and Management Case 2 in the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”) were prepared by Altair management and furnished to J.P. Morgan, and the extrapolations for calendar years 2028 through 2034 were arithmetically calculated by Citi and J.P. Morgan at the direction of the Altair board of directors, with guidance from Altair management, based on Management Case 1 and Management Case 2 and were reviewed and approved for J.P. Morgan’s use by the Altair board of directors (as further described in the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”). Altair does not publicly disclose internal management projections of the type provided to J.P. Morgan in connection with J.P. Morgan’s analysis of the merger, and the financial projections were not prepared with a view toward public disclosure. The financial projections were based on numerous variables and assumptions that are inherently uncertain and may be beyond the control of Altair management, including, without limitation, factors related to general economic and competitive conditions and prevailing interest rates. Accordingly, actual results could vary significantly from those set forth in the financial projections. For more information regarding the financial projections, please refer to the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information.”

J.P. Morgan’s opinion was necessarily based on economic, market and other conditions as in effect on, and the information made available to J.P. Morgan as of, the date of such opinion. J.P. Morgan’s opinion noted that subsequent developments may affect J.P. Morgan’s opinion, and that J.P. Morgan does not have any obligation to update, revise, or reaffirm such opinion. J.P. Morgan’s opinion was limited to the fairness, from a financial point of view, of the merger consideration to be paid to holders of Altair common stock in the merger, and J.P. Morgan expressed no opinion as to the fairness of any consideration to the holders of any other class of securities, creditors or other constituencies of Altair or the underlying decision by Altair to engage in the merger. Furthermore, J.P. Morgan expressed no opinion with respect to the amount or nature of any compensation to any officers, directors or employees of any party to the merger, or any class of such persons relative to the merger consideration to be paid to holders of Altair common stock in the merger or with respect to the fairness of any such compensation.

The terms of the merger agreement, including the merger consideration, were determined through arm’s-length negotiations between Altair and Siemens Industry, and the decision to enter into the merger agreement was solely that of the Altair board of directors. J.P. Morgan’s opinion and financial analyses were only one of the many factors considered by the Altair board of directors in its evaluation of the merger and should not be viewed as determinative of the views of the Altair board of directors or management with respect to the merger or the merger consideration.

In accordance with customary investment banking practice, J.P. Morgan employed generally accepted valuation methodology in rendering its opinion to the Altair board of directors on October 30, 2024 and contained in

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the presentation delivered to the Altair board of directors on such date in connection with the rendering of such opinion and this summary does not purport to be a complete description of the analyses or data presented by J.P. Morgan. Some of the summaries of the financial analyses include information presented in tabular format. The tables are not intended to stand alone, and in order to more fully understand the financial analyses used by J.P. Morgan, the tables must be read together with the full text of each summary. Considering the data set forth below without considering the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of J.P. Morgan’s analyses.

Public Trading Multiples. Using publicly available information, J.P. Morgan compared selected financial data of Altair with similar data for selected publicly traded companies engaged in businesses which J.P. Morgan judged to be analogous to the business of Altair. The companies selected by J.P. Morgan were:

These companies were selected, among other reasons, because they are publicly traded companies with operations and businesses that, for purposes of J.P. Morgan’s analysis, were considered similar to those of Altair. However, certain of these companies may have financial and operating characteristics that are materially different from those of Altair. The analyses necessarily involve complex considerations and judgments concerning differences in financial and operational characteristics of the companies involved and other factors that could affect the selected companies differently than they would affect Altair.

Using publicly available information from company filings, Wall Street estimates and FactSet as of October 29, 2024, J.P. Morgan calculated, for each selected company, the multiple of the firm value (the “FV”) (calculated as the market value of the company’s common stock on a fully diluted basis, plus or minus, as applicable, net debt or net cash and cash equivalents) to the analyst consensus estimates of calendar year 2025 revenues for the applicable company (the “FV/2025E revenue multiple”).

The following table presents the results of this analysis:

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Based on the results of this analysis and J.P. Morgan’s professional judgment and experience, J.P. Morgan selected a FV/2025E revenue multiple reference range for Altair of 9.0x to 12.0x. J.P. Morgan then applied this reference range to Altair’s projected revenue for the calendar year 2025 as set forth in each of Management Case 1 and Management Case 2, which were discussed with, and approved by, the Altair board of directors for the use by J.P. Morgan in connection with its financial analyses. These analyses indicated a range of firm values, which was then adjusted to take into account Altair’s net cash of $495 million, including $513 million of cash and cash equivalents and $19 million of pension liabilities, obtained from Altair management as part of the financial projections, calculated as of September 30, 2024, to derive ranges of implied per share equity value, on a fully diluted basis, for Altair common stock (rounded to the nearest $0.50) of approximately $78.00 to $101.00 for Management Case 1 and $79.00 to $102.50 for Management Case 2. J.P. Morgan compared this to the merger consideration of $113.00 per share of Altair common stock.

Selected Transaction Analysis. Using publicly available information from company filings, Wall Street estimates and FactSet, J.P. Morgan examined selected transactions involving businesses that J.P. Morgan judged to be sufficiently analogous to Altair’s business (or aspects thereof) based on J.P. Morgan’s experience and familiarity with the industries in which Altair operates.

J.P. Morgan calculated, for each selected transaction, the multiple of the target company’s FV implied by the consideration paid for the target company in the respective transaction divided by the target company’s estimated revenue for the twelve months immediately following the announcement of the applicable transaction (the “FV/NTM revenue multiple”).

The following transactions were selected by J.P. Morgan as relevant to the evaluation of the merger and the FV/NTM revenue multiple for each such transaction are as indicated in the following table:

None of the selected transactions reviewed was identical to the merger. However, the selected transactions were chosen by J.P. Morgan because J.P. Morgan judged certain aspects of the transactions, for purposes of J.P. Morgan’s analysis, to be similar to the merger. The analyses necessarily involve complex considerations and judgments concerning differences in financial and operational characteristics of the companies involved and other factors that could affect the transactions differently than they would affect the merger.

Based on the results of this analysis and J.P. Morgan’s professional judgment and experience, J.P. Morgan selected a FV/NTM revenue multiple reference range for Altair of 9.0x to 16.0x. J.P. Morgan then applied this reference range to Altair’s projected revenues for the next twelve months beginning on September 30, 2024, which were calculated as the sum of (i) 25% of Altair’s projected revenues for calendar year 2024 and (ii) 75% of Altair’s projected revenues for calendar year 2025, in each case as set forth in Management Case 1 and Management Case 2, both of which were discussed with, and approved by, the Altair board of directors for the use by J.P. Morgan in connection with its financial analyses. The analysis indicated a range of firm values for Altair, which was then adjusted to take into account Altair’s net cash of $495 million, including $513 million of cash and cash equivalents and $19 million of pension liabilities, obtained from Altair management as part of the financial projections, calculated as of September 30, 2024, which further indicated a range of implied per share equity value, on a fully diluted basis, for Altair common stock (rounded to the nearest $0.50) of approximately

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$76.00 to $128.50 for Management Case 1 and $77.00 to $130.00 for Management Case 2. J.P. Morgan compared this to the merger consideration of $113.00 per share of Altair common stock.

Discounted Cash Flow Analysis. J.P. Morgan conducted a discounted cash flow analysis for the purpose of determining the fully diluted equity value per share for Altair common stock. J.P. Morgan calculated the unlevered free cash flows that Altair is expected to generate from September 30, 2024 through calendar year 2034 based upon both Management Case 1 and the related extrapolations therefrom and Management Case 2 and the related extrapolations therefrom, which were discussed with, and approved by, the Altair board of directors for the use by J.P. Morgan in connection with its financial analyses. The unlevered free cash flow for purposes of the discounted cash flow analysis was calculated as adjusted EBITDA (as defined in the section titled “The Merger (Proposal 1)—Certain Unaudited Projected Financial Information”) less cash tax expenses, changes in net working capital, capital expenditures and stock-based compensation provided by Altair management. J.P. Morgan also calculated a range of terminal values of Altair at the end of this period by applying perpetual growth rates ranging from 3.0% to 4.0%, with such perpetual growth rates range determined based on J.P. Morgan’s professional judgment and experience, to estimates of unlevered free cash flows for Altair in calendar year 2034, based on both Management Case 1 and the related extrapolations therefrom and Management Case 2 and the related extrapolations therefrom. J.P. Morgan then discounted such unlevered free cash flow estimates and the range of terminal values to present value as of September 30, 2024 using discount rates ranging from 7.5% to 9.5%, which range was chosen by J.P. Morgan based upon an analysis of the weighted average cost of capital of Altair. The present values of such unlevered free cash flow estimates and the range of terminal values were then adjusted for Altair’s net cash of $495 million, including $513 million of cash and cash equivalents and $19 million of pension liabilities, obtained from Altair management as part of the financial projections, calculated as of September 30, 2024, to derive implied equity values per share of Altair common stock on a fully diluted basis. This analysis indicated a range of implied per share equity value, on a fully diluted basis, for Altair common stock (rounded to the nearest $0.50) of approximately $63.00 to $109.50 for Management Case 1 and the related extrapolations therefrom and $69.00 to $121.00 for Management Case 2 and the related extrapolations therefrom, which J.P. Morgan compared to the merger consideration of $113.00 per share of Altair common stock.

Other Information. J.P. Morgan observed certain additional information for reference purposes only and not as a component of its fairness analysis:

Miscellaneous. The foregoing summary of certain material financial analyses does not purport to be a complete description of the analyses or data presented by J.P. Morgan. The preparation of a fairness opinion is a

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complex process and is not necessarily susceptible to a partial analysis or summary description. J.P. Morgan believes that the foregoing summary and its analyses must be considered as a whole and that selecting portions of the foregoing summary and these analyses, without considering all of its analyses as a whole, could create an incomplete view of the processes underlying the analyses and its opinion. As a result, the ranges of valuations resulting from any particular analysis or combination of analyses described above were merely utilized to create points of reference for analytical purposes and should not be taken to be the view of J.P. Morgan with respect to the actual value of Altair. The order of analyses described does not represent the relative importance or weight given to those analyses by J.P. Morgan. In arriving at its opinion, J.P. Morgan did not attribute any particular weight to any analyses or factors considered by it and did not form an opinion as to whether any individual analysis or factor (positive or negative), considered in isolation, supported or failed to support its opinion. Rather, J.P. Morgan considered the totality of the factors and analyses performed in determining its opinion.

Analyses based upon forecasts of future results are inherently uncertain, as they are subject to numerous factors or events beyond the control of the parties and their advisors. Accordingly, forecasts and analyses used or made by J.P. Morgan are not necessarily indicative of actual future results, which may be significantly more or less favorable than suggested by those analyses. Moreover, J.P. Morgan’s analyses are not and do not purport to be appraisals or otherwise reflective of the prices at which businesses actually could be acquired or sold. None of the selected companies reviewed as described in the above summary is identical to Altair, and none of the selected transactions reviewed was identical to the merger. However, the companies selected were chosen because they are publicly traded companies with operations and businesses that, for purposes of J.P. Morgan’s analysis, may be considered similar to those of Altair. The transactions selected were similarly chosen because their participants, size and other factors, for purposes of J.P. Morgan’s analysis, may be considered similar to the merger. The analyses necessarily involve complex considerations and judgments concerning differences in financial and operational characteristics of the companies involved and other factors that could affect the companies compared to Altair and the transactions compared to the merger. 

As a part of its investment banking business, J.P. Morgan and its affiliates are continually engaged in the valuation of businesses and their securities in connection with mergers and acquisitions, investments for passive and control purposes, negotiated underwritings, secondary distributions of listed and unlisted securities, private placements, and valuations for corporate and other purposes. J.P. Morgan was selected to advise Altair with respect to the merger and deliver an opinion to the Altair board of directors with respect to the merger on the basis of, among other things, such experience and its qualifications and reputation in connection with such matters and its familiarity with Altair and the industries in which it operates.

For services rendered in connection with the merger and the delivery of its opinion, Altair has agreed to pay J.P. Morgan a fee currently estimated to be approximately $63.8 million, of which $5.0 million became payable in connection with the delivery of the opinion and has been paid, and the remainder is payable upon the consummation of the merger. In addition, Altair has agreed to reimburse J.P. Morgan for its documented reasonable out-of-pocket expenses incurred in connection with its services, including the reasonable fees and disbursements of counsel, and will indemnify J.P. Morgan against certain liabilities arising out of J.P. Morgan’s engagement. During the two years preceding the date of J.P. Morgan’s opinion, neither J.P. Morgan nor any of its affiliates have had any material financial advisory or other material commercial or investment banking relationships with Siemens Industry or Siemens AG. During the two years preceding the date of J.P. Morgan’s opinion, J.P. Morgan and its affiliates have had and continue to have commercial or investment banking relationships with Altair for which J.P. Morgan and such affiliates have received or will receive customary compensation. Such services during such period have included acting as sole bookrunner on a convertible note offering for Altair in June 2022. In addition, J.P. Morgan’s commercial banking affiliate is an agent bank and a lender under outstanding credit facilities of Altair, for which it receives customary compensation or other financial benefits. During the two-year period preceding delivery of its opinion, the aggregate fees recognized by J.P. Morgan from Altair and Siemens AG were approximately $2.0 million and approximately $9.0 million, respectively. In addition, J.P. Morgan and its affiliates hold, on a proprietary basis, less than 1% of the outstanding common stock of each of Altair and Siemens AG. In the ordinary course of their businesses, J.P. Morgan and its affiliates actively trade the debt and equity securities or financial

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instruments (including derivatives, bank loans or other obligations) of Altair or Siemens AG for their own accounts or for the accounts of customers and, accordingly, they likely hold long or short positions in such securities or other financial instruments.

Certain Unaudited Projected Financial Information

While Altair has from time to time provided limited financial guidance to investors, Altair management does not, as a matter of course, otherwise publicly disclose forecasts or internal projections as to future performance due to, among other things, the inherent difficulty of predicting financial performance for future periods and the likelihood that the underlying assumptions and estimates may not be realized. In connection with the review of strategic alternatives, including the merger, Altair senior management prepared and provided certain unaudited non-public financial projections regarding Altair for calendar years 2024 through 2027, reflecting two different cases (“Management Case 1” and “Management Case 2”), to the Altair board of directors. Altair management prepared two different cases to give the Altair board of directors a broader perspective on possible alternative financial outcomes depending on growth rates over time, with Management Case 1 reflecting more conservative assumptions with respect to Altair’s revenue growth and adjusted EBITDA (as defined below) margin expansion and Management Case 2 reflecting comparatively more optimistic assumptions as to revenue growth and adjusted EBITDA margin expansion. Altair management viewed Management Case 1 and Management Case 2 as equally likely. In addition, at the direction of the Altair board of directors, and to facilitate their financial analyses for purposes of rendering their respective opinions to the Altair board of directors, Citi and J.P. Morgan, with guidance from Altair management, arithmetically calculated financial projections for calendar years 2028 through 2034 by extrapolating from Management Case 1 and Management Case 2 based on assumptions with respect to, among others, revenue growth rates and gross margin and EBITDA margin expansion. Such financial projections, including the extrapolations, were approved by the Altair board of directors for use by Citi and J.P. Morgan for purposes of performing their financial analyses in connection with rendering their opinions to the Altair board of directors (as more fully described above under the sections titled “—Opinion of Citi” and “—Opinion of J.P. Morgan”). Management Case 1 and Management Case 2 were also provided to Siemens Industry and Siemens AG in connection with its customary due diligence.

These unaudited financial projections, including Management Case 1 and the related extrapolations therefrom and Management Case 2 and the related extrapolations therefrom, are collectively referred to as the “financial projections.” A summary of the financial projections is included below to give Altair stockholders access to certain information that was considered by the Altair board of directors for purposes of evaluating the merger. These financial projections are not, and should not be viewed as, public guidance or even targets.

The financial projections, while presented with numerical specificity, were based on numerous variables and assumptions, including about future performance, that are inherently uncertain and many of which are beyond Altair’s control. The financial projections reflect numerous estimates, assumptions and judgments made by Altair management that Altair management considered to be reasonable based on information available at the time the financial projections were developed, with respect to industry performance and competition, general business, economic, regulatory, market and financial conditions, other future events and matters specific to Altair’s business, all of which are difficult to predict and many of which are beyond Altair’s control. There can be no assurances that the financial projections accurately reflect future trends or accurately estimate Altair’s future financial and operating performance. The financial projections also reflect assumptions as to certain business decisions that are subject to change. Important factors that may affect actual results and cause the financial projections not to be achieved include, but are not limited to, risks and uncertainties relating to Altair’s business (including the ability to achieve strategic goals, objectives and targets over the applicable periods), industry performance, general business, economic and regulatory conditions, changes in actual or projected cash flows, competitive pressures and changes in tax laws or accounting treatment and other factors described in or referenced under the section titled “Cautionary Statement Regarding Forward-Looking Statements” and those risks and uncertainties detailed in Altair’s public filings with the SEC. Further, the financial projections cover multiple years and by their nature become subject to greater uncertainty with each successive year. Accordingly,

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there can be no assurance that the financial projections will be realized, and actual results may vary materially from those shown. Modeling and forecasting the future performance of an engineering software company is a highly speculative endeavor. Since the financial projections cover a long period of time, the financial projections by their nature are unlikely to anticipate each circumstance that will have an effect on the commercial value of Altair’s products and services.

The financial projections were not prepared with a view toward public disclosure and, accordingly, do not necessarily comply with published guidelines of the SEC or the guidelines established by the American Institute of Certified Public Accountants for preparation or presentation of prospective financial information or generally accepted accounting principles in the United States (“GAAP”).

The financial projections are the responsibility of Altair’s management. Neither Ernst & Young LLP (“EY”), Altair’s independent registered public accounting firm, nor any other independent accountant, has audited, reviewed, examined, compiled, performed any other assurance procedures or expressed any form of assurance with respect to the financial projections incorporated by reference in this proxy statement. The report of EY incorporated by reference from Altair’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023, relates to Altair’s historical audited financial statements and does not extend to the financial projections and should not be read to do so.

The financial projections are not being included in this proxy statement in order to influence any Altair stockholder’s decision as to whether or not to approve the merger or whether or not to seek appraisal rights with respect to shares of Altair common stock held by such stockholder. The summary of the financial projections is being included in this proxy statement solely because these financial projections were made available to the Altair board of directors, Citi, J.P. Morgan and Siemens Industry.

The financial projections do not take into account any circumstances or events occurring after the date they were prepared, including the announcement of the merger, merger-related expenses or any changes to operation that may be implemented in connection with the pendency, or following the consummation, of the merger. The financial projections also do not take into account the effect of any failure of the merger to close and should not be viewed as accurate or continuing in that context.

The inclusion of the financial projections in this proxy statement should not be regarded as an indication that Altair, Citi, J.P. Morgan or any of their respective affiliates, advisors or representatives considered or consider the financial projections to be predictive of actual future events, and the financial projections should not be relied on as such. None of Altair, Citi, J.P. Morgan or any of their respective affiliates, advisors, officers, directors or representatives can give any assurance that actual results will not differ from these financial projections, and none of them undertakes any obligation to update or otherwise revise or reconcile the financial projections to reflect circumstances existing after the date such financial projections were generated or to reflect the occurrence of future events even in the event that any or all of the assumptions underlying the financial projections are shown to be in error or no longer appropriate. Altair does not intend to make publicly available any update or other revisions to the financial projections, except as required by law. None of Altair, Citi, J.P. Morgan or any of their respective affiliates, advisors, officers, directors or representatives has made or makes any representation to any stockholder or other investor regarding the ultimate performance of Altair compared to the information contained in the financial projections or that the projected results will be achieved.

Altair stockholders are cautioned not to place undue, if any, reliance on the financial projections included in this proxy statement.

The financial projections incorporate certain financial measures which are not GAAP measures, including adjusted EBITDA and unlevered free cash flow (in each case, as defined below). Such financial measures should not be considered in isolation from, or as a substitute for, financial information presented in accordance with GAAP. Altair’s calculations of these financial measures may differ from others in its industry and are not necessarily comparable with information presented under similar captions used by other companies. Financial

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measures provided to a financial advisor are excluded from the SEC’s definition of non-GAAP financial measures and therefore are not subject to SEC rules regarding disclosures of non-GAAP financial measures, which may otherwise require a reconciliation of a non-GAAP financial measure to a GAAP financial measure to be presented. Reconciliations of these financial measures were not relied upon by Citi or J.P. Morgan for purposes of performing their respective financial analyses in connection with rendering their respective opinions to the Altair board of directors (as described in the sections titled “—Opinion of Citi” and “—Opinion of J.P. Morgan”) or by the Altair board of directors. Accordingly, a reconciliation of the financial measures included in the financial projections is not provided.

Subject to the foregoing qualifications, a summary of the financial projections is set forth below:

Management Case 1 and Related Extrapolations (Unaudited)

Management Case 2 and Related Extrapolations (Unaudited)

For additional information on Altair’s actual results and historical financial information, see the section titled “Where You Can Find More Information.”

Interests of Altair’s Directors and Executive Officers in the Merger

In considering the recommendation of the Altair board of directors that Altair stockholders vote “FOR” (1) the merger agreement proposal and (2) merger-related compensation proposal, Altair stockholders should be aware that the directors and executive officers of Altair have interests in the merger that may be different from, or in addition to, those of Altair stockholders generally.

These interests are described below, and certain of them are quantified below. The Altair board of directors was aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement and the merger, in approving the merger agreement, and in recommending the approval of the merger agreement by the Altair stockholders.

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Treatment of Altair Equity Awards

Each of Altair’s directors and executive officers holds Altair options and/or RSUs. At the effective time, the outstanding Altair equity awards will be treated as follows:

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The table below sets forth the number of outstanding Altair stock options and RSUs held by each of Altair’s executive officers and non-employee directors as of November 6, 2024, whether vested or unvested, and an estimate of the value of such awards (on a pre-tax basis) based on a per share price of Altair common stock of $113.00 (and with respect to stock options, the value is measured based on the excess of $113.00 over the applicable exercise price). Depending on the date upon which the closing of the merger actually occurs, certain Altair stock options and RSUs that are unvested as of the date of this proxy statement and that are included in the table below may vest pursuant to their terms, without regard to the merger. For additional information regarding shares of Altair common stock held by Altair executive officers and non-employee directors, see the section titled “Security Ownership of Certain Beneficial Owners and Management.”

These amounts do not attempt to forecast any additional equity award grants, issuances or forfeitures that may occur prior to the closing of the merger following the date of this proxy statement. Although it is anticipated that the above-mentioned executive officers will receive additional grants of restricted stock units during the first quarter of 2025 consistent with prior practice, such grants have not actually been made as of the date of this proxy statement and the amounts thereof have not yet been approved by the Compensation Committee of the Altair board of directors; accordingly, such grants have been excluded from the presentation set forth above. As a result of the foregoing assumptions, which may or may not actually occur or be accurate on the relevant date, the actual amounts, if any, to be received by Altair’s executive officers and non-employee directors may materially differ from the amounts set forth above.

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Treatment of Altair Employee Stock Purchase Plan

The Altair Engineering Inc. 2021 Employee Stock Purchase Plan (the “ESPP”) will be frozen and suspended at the end of the offering period that is in progress as of October 30, 2024 and no new offering periods will commence under the ESPP at any time on or after October 30, 2024. No new participants will commence participation in the ESPP following October 30, 2024, and no participant in the ESPP will increase his or her payroll contribution rate in effect as of October 30, 2024 or make separate non-payroll contributions following October 30, 2024. The ESPP will terminate no later than immediately prior to the effective time.

Existing Altair Severance Agreements

Altair is party to a severance agreement with each of its executive officers other than Mr. Jeff Marraccini. Pursuant to the severance agreements, if during the period commencing on October 30, 2024 and ending 12 months after a “change of control,” the executive’s employment is terminated by Altair without “cause” or by the executive for “good reason” (as such terms are defined in the severance agreements), in each case, subject to the executive’s execution and non-revocation of a general release of claims, the executive is entitled to:

For purposes of the severance agreements:

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Indemnification and Insurance

Under the merger agreement, for a period of six years after the effective time, Siemens Industry must cause the surviving corporation to indemnify and hold harmless to the fullest extent permitted by applicable law and the organizational documents of Altair or its subsidiaries, the present and former directors, officers and agents of Altair and its subsidiaries and any individuals serving in such capacity at or with respect to other persons at Altair’s or its subsidiaries’ request, against any losses, damages, liabilities, costs, expenses (including attorneys’ fees), judgments, fines, penalties and amounts paid in settlement (including all interest, assessments and other charges paid or payable in connection with or in respect of any thereof) in respect of the persons having served in such capacity prior to the effective time.

In addition, for a period of six years following the effective time, Siemens Industry is required to maintain in effect provisions in the organizational documents of the surviving corporation and its subsidiaries regarding elimination of liability of directors, indemnification of directors, officers and agents and advancement of fees, costs and expenses that are no less advantageous to the intended beneficiaries than the corresponding provisions that were in existence as of October 30, 2024.

From and after the effective time, Siemens Industry is required to, and will cause the surviving corporation and its subsidiaries to, honor and comply with their respective obligations under any indemnification agreement with any director or officer of Altair or its subsidiaries, and not amend, repeal or otherwise modify any such agreement in any manner that would adversely affect any rights of such persons.

Prior to the effective time, Altair will (or if Altair is unable to, Siemens Industry will cause the surviving corporation to) purchase a directors’ and officers’ liability insurance and fiduciary liability insurance “tail” policy for a period of six years after the effective time with respect to matters arising at or prior to the effective time with terms, conditions, retentions and limits of liability that are no less favorable than the coverage provided under Altair’s existing policies as of October 30, 2024, with a one-time cost not in excess of 350% of the last aggregate annual premium paid by Altair for its directors’ and officers’ liability insurance and fiduciary liability insurance prior to October 30, 2024, and if the cost of such “tail” insurance policy would otherwise exceed such amount, the surviving corporation must purchase a policy with the greatest coverage available for a cost not exceeding such amount.

See the sections titled “The Merger (Proposal 1)—Interests of Altair’s Directors and Executive Officers in the Merger—Indemnification and Insurance” and “The Merger Agreement—Directors’ and Officers’ Indemnification and Insurance.”

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Quantification of Potential Payments and Benefits to Altair’s Named Executive Officers in Connection with the Merger

The information set forth below is required by Item 402(t) of Regulation S-K regarding compensation that is based on or otherwise relates to the merger that Altair’s named executive officers could receive in connection with the merger. Such amounts have been calculated assuming that:

The payments and benefits described below are calculated based on, to the extent applicable, the terms of the merger agreement and each named executive officer’s existing severance agreement. See sections above under “—Treatment of Altair Equity Awards” and “—Existing Altair Severance Agreements,” for a description of the treatment of the equity awards held by the named executive officers and the terms of their severance agreements. In addition, certain equity awards held by the named executive officers may vest in accordance with their terms prior to the merger. These amounts do not attempt to forecast any additional equity award grants, issuances or forfeitures that may occur after the date of this proxy statement but before the effective time. Although it is anticipated that the executive officers named below will receive additional grants of restricted stock units during the first quarter of 2025 consistent with prior practice, such grants have not actually been made as of the date of this proxy statement and the amounts thereof have not yet been approved by the Compensation Committee of the Altair board of directors; accordingly, such grants have been excluded from the presentation set forth below. As a result of the foregoing assumptions, which may or may not actually occur or be accurate on the relevant date, including the assumptions described in the footnotes to the table, the actual amounts, if any, to be received by Altair’s named executive officers may materially differ from the amounts set forth below.

Golden Parachute Compensation

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280G Mitigation Actions

In order to mitigate the potential impact of Sections 280G and 4999 of the Code, the Altair board of directors approved the following:

Regulatory Clearances and Approvals Required for the Merger

The completion of the merger is conditioned on, among other things, the required regulatory approvals having been obtained or received (or, as applicable, the waiting periods with respect thereto having expired or been terminated), including the expiration or termination of any applicable waiting period under the HSR Act.

Subject to the terms and conditions of the merger agreement, each of Altair and Siemens Industry has agreed to take, or cause to be taken (including by causing their affiliates to take), all actions and to do, or cause to

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be done, all things necessary, proper or advisable under applicable law to consummate the transactions contemplated by the merger agreement as promptly as practicable, including preparing and filing as promptly as practicable with any governmental authority or other third party all documentation to effect all necessary, proper or advisable filings, notices, petitions, statements, registrations, submissions of information, applications and other documents and obtaining and maintaining all approvals, consents, registrations, permits, authorizations and other confirmations required to be obtained from any governmental authority or other third party that are necessary, proper or advisable to consummate the merger, including the required regulatory approvals.

The merger cannot be completed until all applicable waiting periods (and any extensions thereof) under the HSR Act relating to the merger, and any commitment to, or agreement with, any governmental authority to delay the consummation of, or not to consummate before a certain date, the merger, have expired or been terminated, and the required regulatory approvals have been obtained or received or, as applicable, the waiting periods with respect thereto have expired or been terminated. There can be no assurance that a challenge to the merger on regulatory grounds by a governmental authority or private party will not be made or, if such a challenge is made, that it would not be successful.

If any objections are asserted with respect to the transactions contemplated by the merger agreement under the HSR Act, any other applicable competition law or in connection with any required regulatory approval, or if any proceeding under competition laws is instituted or threatened by any governmental authority challenging any of the transactions contemplated by the merger agreement, Siemens Industry and Altair have agreed to use reasonable best efforts to resolve such objections as promptly as practicable.

Each of Altair and Siemens Industry has agreed to oppose (1) any administrative or judicial proceeding that is initiated or threatened to be initiated challenging the merger agreement or the consummation of the transactions contemplated thereby as violative of any competition law (including seeking to have any stay or temporary restraining order entered by any court or other governmental authority vacated or reversed) and (2) any request for the entry of, and to seek to have vacated or terminated, any order in connection with any competition law that would reasonably be expected to restrain, prevent or materially delay the consummation of the transactions contemplated by the merger agreement, including in the case of either (1) or (2), by defending through litigation any proceeding brought by any governmental authority pursuant to any competition law, and vigorously pursuing all available avenues of administrative and judicial appeal. However, in no event will Siemens Industry or its subsidiaries or affiliates be required to take any remedy action, except to the extent that such remedy action would not, and would not reasonably be expected to, individually or in the aggregate, result in a burdensome condition. The reasonable best efforts of Siemens Industry will include taking any remedy action that would not, and would not reasonably be expected to, individually or in the aggregate, result in a burdensome condition.

Altair has agreed not to, and has agreed to cause its subsidiaries not to, offer, propose, negotiate, agree to, commit to, effect or take any remedy action without the prior written consent of Siemens Industry, and Altair has agreed to, and has agreed to cause its subsidiaries to, offer, propose, negotiate, agree to, commit to, effect and take any remedy action if so directed by Siemens Industry in connection with obtaining the required regulatory approvals; provided, that any remedy action is conditioned on the closing of the merger. If requested by Siemens Industry, Altair must divest, hold separate or take or commit to take any action that limits its freedom of action with respect to, or its ability to retain, any of the businesses, services or assets of Altair or its subsidiaries, provided that any such action is conditioned on the consummation of the merger and the other transactions contemplated by the merger agreement.

Neither Altair nor Siemens Industry will take any action if such action would (1) make it materially more likely that there would arise any impediments under any competition law or other applicable law that may be asserted by the FTC, the Antitrust Division, any State Attorney General or any other governmental authority to the consummation of the merger and the other transactions contemplated by the merger agreement, as promptly as practicable or (2) impose any material delay in the expiration of any waiting period or obtaining of any approval from any governmental authority necessary to consummate the transactions contemplated by the merger agreement.

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On November 15, 2024, each of Altair and Siemens Industry filed a notification of the proposed merger with the FTC and the Antitrust Division under the HSR Act. The waiting period expired on December 16, 2024 at 11:59 p.m., Eastern Time.

In addition, Altair and Siemens Industry will prepare and, at least 65 days prior to the closing date, file with the DDTC, in accordance with ITAR at 22 C.F.R. 122.4(b), a notification regarding the merger and the other transactions contemplated in the merger agreement.

For more information about regulatory clearance relating to the merger, see the section titled “The Merger Agreement—Conditions to the Merger.”

Although the parties expect that the required regulatory approvals will be obtained, the parties cannot assure you that such approvals will be timely obtained or obtained at all or that the granting of regulatory approvals will not involve the imposition of additional conditions on the completion of the merger, or a commitment or agreement to take remedial actions, including divesting assets or businesses, creating, modifying or transferring contractual rights or obligations or entering into supply or services agreements. Any such requirements could result in the conditions to the merger not being satisfied.

Accounting Treatment

The merger will be accounted for as a “purchase transaction” for financial accounting purposes.

Delisting and Deregistration of Altair Common Stock

Prior to the effective time, Altair has agreed to cooperate with Siemens Industry and use reasonable best efforts to take, or cause to be taken, all actions, and do or cause to be done all things, reasonably necessary, proper or advisable on its part under applicable laws and the rules and policies of Nasdaq to enable delisting by the surviving corporation of the Class A common stock from Nasdaq and the deregistration of the Class  A common stock under the Exchange Act as promptly as practicable after the effective time.

Appraisal Rights of Altair Stockholders

Altair stockholders who do not vote in favor of approval of the merger agreement proposal, who continuously hold their shares of Altair common stock and who otherwise comply precisely with the applicable provisions of Section 262 of the DGCL will be entitled to seek appraisal of the fair value of their shares of Altair common stock, as determined by the Delaware Court of Chancery, if the merger is completed, in lieu of receiving the merger consideration in respect of such shares. The “fair value” of your shares of Altair common stock as determined by the Delaware Court of Chancery could be greater than, the same as or less than the value of the merger consideration that you would otherwise be entitled to receive under the terms of the merger agreement. Altair stockholders who wish to exercise the right to seek an appraisal of their shares must so advise Altair by submitting a written demand for appraisal in the form described in this proxy statement prior to the vote to approve the merger agreement proposal, and must otherwise follow the procedures prescribed by Section 262 of the DGCL. A person having a beneficial interest in shares of Altair common stock held of record in the name of another person, such as a nominee or intermediary, must act promptly to cause the record holder to follow the steps summarized in this proxy statement and in a timely manner to perfect appraisal rights.

The text of Section 262 of the DGCL is attached as Annex F to this proxy statement. You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising appraisal rights, Altair stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel and their financial advisors. Failure to strictly comply with these provisions may result in the loss of appraisal rights.

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Litigation Related to the Merger

As of the date of this proxy statement, there are no pending lawsuits challenging the merger. However, potential plaintiffs may file lawsuits challenging the merger. The outcome of any future litigation is uncertain.

Such litigation, if not resolved, could prevent or delay consummation of the merger and result in substantial costs to Altair, including any costs associated with the indemnification of directors and officers. One of the conditions to the consummation of the merger is the absence of any order or applicable law issued by any governmental authority of competent jurisdiction that prohibits, renders illegal or enjoins the consummation of the merger whether on a temporary, preliminary or permanent basis. Therefore, if a plaintiff were successful in obtaining an injunction prohibiting the consummation of the merger on the agreed-upon terms, then such injunction may prevent the merger from being consummated, or from being consummated within the expected time frame.

Altair has agreed to give Siemens Industry a reasonable opportunity to participate in (at Siemens Industry’s expense), but not control, the defense, settlement or prosecution of any stockholder litigation against the Company or any of its directors or officers relating to the merger agreement, the merger or any other transactions contemplated by the merger agreement. Further, Altair has agreed not to settle or offer to settle any stockholder litigation without Siemens Industry’s prior written consent (such consent not to be unreasonably withheld, delayed or conditioned).

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THE MERGER AGREEMENT

The following describes the material provisions of the merger agreement, which is attached as Annex A to this proxy statement and is incorporated by reference herein. The summary of the material provisions of the merger agreement below and elsewhere in this proxy statement is qualified in its entirety by reference to the merger agreement. This summary does not purport to be complete and may not contain all of the information about the merger agreement that is important to you. Altair encourages you to read carefully the merger agreement in its entirety before making any decisions regarding the merger as it is the legal document governing the merger.

Explanatory Note Regarding the Merger Agreement

The merger agreement and this summary of its terms have been included to provide you with information regarding the terms of the merger agreement. Altair is responsible for considering whether additional disclosure of material information is required to make the statements in this proxy statement not misleading. Factual disclosures about Altair contained in this proxy statement or Altair’s public reports filed with the SEC may supplement, update or modify the factual disclosures about Altair contained in the merger agreement and described in this summary. The representations, warranties and covenants made in the merger agreement by Siemens Industry, Merger Sub and Altair are qualified and subject to important limitations agreed to by the parties to the merger agreement in connection with negotiating the terms of the merger agreement, including being qualified by the disclosure schedules to the merger agreement. In particular, in your review of the representations and warranties contained in the merger agreement and described in this summary, it is important to bear in mind that the representations and warranties were made solely for the benefit of the parties to the merger agreement, and were negotiated with the principal purpose of allocating risk between the parties to the merger agreement, rather than establishing matters as facts. The representations and warranties may also be subject to a contractual standard of materiality that may be different from that generally relevant to stockholders or applicable to reports and documents filed with the SEC, and in some cases are qualified by confidential disclosures that were made by each party to the other, which disclosures are not publicly disclosed. The representations and warranties in the merger agreement will not survive the completion of the merger.

Altair stockholders should not rely on representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of Siemens Industry, Merger Sub, Altair or any of their respective subsidiaries or affiliates. Moreover, information concerning the subject matter of the representations and warranties may have changed since October 30, 2024. For the foregoing reasons, the representations, warranties and covenants or any descriptions of those provisions should not be read alone, but instead should be read together with the information provided elsewhere in this proxy statement and in the documents incorporated by reference into this proxy statement. See the section titled “Where You Can Find More Information.”

Structure of the Merger

The merger agreement provides that, upon the terms and subject to the conditions set forth therein and in accordance with the DGCL, at the effective time, Merger Sub will merge with and into Altair, with Altair surviving as a wholly owned subsidiary of Siemens Industry.

Closing and Effective Time of the Merger

Unless another place, time or date is mutually agreed to in writing by Altair and Siemens Industry, the closing of the merger will occur as soon as possible, but in any event no later than four business days after the date the closing conditions set forth in the merger agreement (other than conditions that by their nature are to be satisfied at the closing of the merger, but subject to the satisfaction or, to the extent permissible, waiver of those conditions at the closing of the merger) have been satisfied or, to the extent permissible, waived by the party or

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parties entitled to the benefit of such conditions. The merger will become effective at such time as the certificate of merger is duly filed with the Secretary of State of the State of Delaware in accordance with the relevant provisions of the DGCL (or at such later time as may be specified in the certificate of merger). As of the date of this proxy statement, we expect to complete the merger in the second half of 2025. However, completion of the merger is subject to the satisfaction or waiver of the conditions to the completion of the merger, which are described below, and it is possible that factors outside the control of Altair and Siemens Industry could delay the completion of the merger or prevent it from being completed at all. There may be a substantial amount of time between the special meeting and the completion of the merger. We expect to complete the merger promptly following the receipt of all required regulatory approvals.

Effect of the Merger on Altair Common Stock

Conversion of Altair Common Stock

At the effective time, each share of Altair common stock (including any Altair common stock to the extent issued in accordance with the terms of the merger agreement and the convertible notes indenture, but excluding (i) Altair common stock held by Altair as treasury stock or owned by Siemens Industry, Merger Sub or any other subsidiary of Siemens Industry immediately prior to the effective time and (ii) Altair common stock with respect to which appraisal rights are properly demanded and not withdrawn or lost under the DGCL) outstanding immediately prior to the effective time will automatically be converted into the right to receive $113.00 in cash, without interest.

Cancellation of Certain Altair Common Stock

At the effective time, each share of Altair common stock that is held in treasury by Altair or owned by Siemens Industry, Merger Sub or any other subsidiary of Siemens Industry immediately prior to the effective time will automatically be canceled and will cease to exist, and no consideration will be delivered in exchange for such shares.

Shares of Merger Sub

At the effective time, each share of common stock of Merger Sub outstanding immediately prior to the effective time will be converted into and become one share of common stock of the surviving corporation and will constitute the only outstanding shares of capital stock of the surviving corporation.

Treatment of Altair Equity Awards

Altair Stock Options

Each vested option that is outstanding and unexercised as of immediately prior to the effective time and each director option will vest (to the extent unvested) and be canceled and converted into the right to receive an amount in cash (without interest) equal to (x) the number of shares of Class A common stock subject to such vested option or director option immediately prior to the effective time multiplied by (y) the excess of the merger consideration over the per share exercise price applicable to such vested option or director option, less any applicable withholding taxes.

Each unvested option that is outstanding and unexercised as of immediately prior to the effective time will be canceled and converted into the right to receive a future amount in cash equal to (x) the number of shares of Class A common stock subject to such unvested option immediately prior to the effective time multiplied by (y) the excess of the merger consideration over the per share exercise price applicable to such unvested option, which cash award will continue to vest following the effective time, subject to the holder’s continued employment or service through the last day of the calendar quarter preceding the quarter in which such unvested option would have otherwise vested in accordance with the vesting schedule in effect immediately prior to the

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effective time (had the holder remained in continuous employment or service through such date), and will be paid less any applicable withholding taxes by the surviving corporation or its applicable subsidiary as soon as reasonably practicable but no later than the next regularly scheduled payroll run of the surviving corporation or its applicable subsidiary that is at least ten business days following the applicable vesting date. Notwithstanding the foregoing, such cash award will (i) accelerate in full and be paid upon a holder’s termination without “cause” (as determined by the surviving corporation) or for “good reason” (to the extent such holder has an agreement or participates in an Altair plan that provides for severance benefits upon a resignation for good reason, and as defined in such agreement or Altair plan) and (ii) accelerate upon any other circumstances set forth in any applicable award agreement, severance agreement or other similar agreement or Altair plan applicable to the holder as of October 30, 2024 (or entered into between October 30, 2024 and the effective time in accordance with the merger agreement), in each case, subject to the holder’s execution of a release of claims in a form prescribed by the surviving corporation. Such cash award will be forfeited without payment upon the holder’s termination of employment or service with the surviving corporation and its subsidiaries for any reason not described in the preceding sentence.

Each stock option of Altair that has a per share exercise price that is equal to or greater than the merger consideration (if any) will be canceled without payment.

Altair RSUs

Each vested RSUs and each director RSU will vest (to the extent unvested) and be canceled and converted into the right to receive an amount in cash equal to (x) the number of shares of Class A common stock subject to such vested RSU or director RSU immediately prior to the effective time multiplied by (y) the merger consideration, less any applicable withholding taxes.

Each unvested RSU will be canceled and converted into the right to receive an amount in cash equal to (x) the number of shares of Class A common stock subject to such unvested RSU immediately prior to the effective time multiplied by (y) the merger consideration, which cash award will continue to vest, subject to the holder’s continued employment or service through the last day of the calendar quarter preceding the quarter in which such unvested RSU would have otherwise vested in accordance with the vesting schedule in effect immediately prior to the effective time (had the holder remained in continuous employment or service through such date), and will be paid less any applicable withholding taxes by the surviving corporation or its applicable subsidiary as soon as reasonably practicable but no later than the next regularly scheduled payroll run of the surviving corporation or its applicable subsidiary that is at least ten business days following the applicable vesting date. Notwithstanding the foregoing, such cash award will (i) accelerate in full and be paid upon a holder’s termination without “cause” (as determined by the surviving corporation) or for “good reason” (to the extent such holder has an agreement or participates in an Altair plan that provides for severance benefits upon a resignation for good reason, and as defined in such agreement or Altair plan) and (ii) accelerate upon any other circumstances set forth in any applicable award agreement, severance agreement or other similar agreement or Altair plan applicable to the holder as of October 30, 2024 (or entered into between October 30, 2024 and the effective time in accordance with the merger agreement), in each case, subject to the holder’s execution of a release of claims in a form prescribed by the surviving corporation. Such cash award will be forfeited without payment upon the holder’s termination of employment or service with the surviving corporation and its subsidiaries for any reason not described in the preceding sentence.

ESPP

The Altair Engineering Inc. 2021 Employee Stock Purchase Plan, as amended from time to time in accordance with its terms, (the “ESPP”) will be frozen and suspended at the end of the offering period that was in progress as of October 30, 2024 (i.e., January 14, 2025) and no new offering periods will commence under the ESPP at any time on or after October 30, 2024. No new participants will commence participation in the ESPP following October 30, 2024, and no participant in the ESPP will be permitted to increase his or her payroll

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contribution rate in effect as of October 30, 2024 or make separate non-payroll contributions on or following October 30, 2024. The ESPP will terminate immediately prior to, and contingent upon, the effective time.

Shares of Dissenting Stockholders

Shares of Altair common stock issued and outstanding immediately prior to the effective time and held by an Altair stockholder who (i) did not vote in favor of the merger agreement proposal or consent in writing thereto and (ii) properly and validly demanded their statutory rights of appraisal in respect of such shares of Altair common stock in accordance with Section 262 of the DGCL will not be converted into, or represent the right to receive, the merger consideration unless such holder fails to perfect, withdraws or otherwise loses the right to appraisal. Instead, such dissenting stockholders will be entitled to receive payment of the appraised value of such shares of Altair common stock in accordance with Section 262 of the DGCL.

If any dissenting stockholder fails to perfect or otherwise effectively withdraws or loses their rights of appraisal, such shares of Altair common stock will thereupon be deemed to have been converted into, and to have become exchangeable for, as of the effective time, the right to receive the merger consideration. For more information regarding appraisal rights, see the section titled “Appraisal Rights of Altair Stockholders.” In addition, a copy of Section 262 of the DGCL is attached as Annex F to this proxy statement.

Governing Documents; Officers and Directors

At the effective time and by virtue of the merger, the certificate of incorporation of Altair, as in effect immediately prior to the completion of the merger, will be amended and restated in its entirety as set forth in Exhibit A to the merger agreement and, as so amended and restated, will be the certificate of incorporation of the surviving corporation until further amended in accordance with Delaware law.

The bylaws of Merger Sub as in effect immediately prior to the effective time will be the bylaws of the surviving corporation (except that references to the name of Merger Sub will be replaced by reference to the name of the surviving corporation) until thereafter amended in accordance with applicable law.

From and after the effective time, until their successors are duly elected or appointed and qualified or until their earlier death, resignation or removal in accordance with the certificate of incorporation and the bylaws of the surviving corporation and applicable law, (i) the directors of Merger Sub at the effective time will be the directors of the surviving corporation and (ii) the officers of Altair at the effective time will be the officers of the surviving corporation.

Exchange and Payment Procedures

Prior to the closing date, Siemens Industry will appoint an exchange agent reasonably acceptable to Altair for the purpose of exchanging for the merger consideration shares of Altair common stock. Prior to the effective time, Siemens Industry will make available, or cause to be made available, to the exchange agent the aggregate merger consideration to be paid in respect of the shares of Altair common stock.

As promptly as practicable after the effective time (but no later than two business days thereafter), Siemens Industry will send, or will cause the exchange agent to send, to each Altair stockholder at the effective time instructions on how to surrender shares of Altair common stock in exchange for the merger consideration.

Each holder of shares of Altair common stock that have been converted into the right to receive the merger consideration will be entitled to receive, upon receipt of an “agent’s message” by the exchange agent (or such other evidence, if any, of transfer as the exchange agent may reasonably request), the merger consideration payable for each share of Altair common stock. Until so surrendered or transferred, each such share will represent from and after the effective time for all purposes only the right to receive such merger consideration. No interest will be paid or will accrue on the cash payable upon surrender of any such shares of Altair common stock.

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If any portion of the merger consideration is to be paid to a person other than the person in whose name the transferred shares of Altair common stock is registered, it will be a condition to such payment that (i) such share be properly transferred and (ii) the person requesting such payment will pay to the exchange agent any transfer or other taxes required as a result of such payment or establish to the satisfaction of the exchange agent that such tax has been paid or is not payable.

Rights of Altair Stockholders Following the Effective Time; Transfers Following the Effective Time

From and after the effective time, all holders of shares of Altair common stock will cease to have any rights as Altair stockholders other than the right to receive the merger consideration upon the surrender of such shares, without interest. From and after the effective time, the stock transfer books of Altair will be closed with respect to all shares of Altair common stock outstanding immediately prior to the effective time.

None of Siemens Industry, the surviving corporation or the exchange agent will be liable to any person with respect to any portion of the merger consideration delivered to a governmental authority if required by any applicable abandoned property, escheat or similar law.

Any portion of the merger consideration made available to the exchange agent (and any interest or other income earned thereon) that remains unclaimed by the holders of Altair common stock 12 months after the effective time will be returned to Siemens Industry, upon demand, and such Altair stockholders must thereafter look only to Siemens Industry for payment of the merger consideration. Further, any portion of the merger consideration that remains undistributed to holders of shares of Altair common stock immediately prior to the date on which the merger consideration would otherwise escheat to or become the property of any governmental entity will, to the extent permitted by applicable law, become the property of Siemens Industry, free and clear of all claims or interest of any person previously entitled to such claims or interest.

Withholding Rights

Siemens Industry, Altair, the surviving corporation and any of their respective affiliates or agents (including the exchange agent) will be entitled to deduct and withhold from any amounts otherwise payable pursuant to the merger agreement such amounts as are required to be deducted or withheld under the Code or any other applicable tax law. Any amounts so deducted or withheld will be paid over to the appropriate taxing authority and be treated for all purposes of the merger agreement as having been paid to the person in respect of which such deduction or withholding was made.

Representations and Warranties

The merger agreement contains customary representations and warranties of the parties. These include representations and warranties of Altair with respect to:

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The merger agreement also contains customary representations and warranties of Siemens Industry. These include representations and warranties with respect to:

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The representations and warranties in the merger agreement do not survive the closing or termination of the merger agreement.

Certain of the representations and warranties made by the parties are qualified as to “knowledge,” “materiality” or “material adverse effect,” as defined in the merger agreement and/or described below and/or speak as of or with respect to a certain date or period of time.

Material Adverse Effect

Many of Altair’s representations and warranties in the merger agreement are qualified by an “Altair material adverse effect” standard (that is, they will not be deemed to be untrue or incorrect unless their failure to be true or correct has had or would reasonably be expected to have, individually or in the aggregate, an Altair material adverse effect). For purposes of the merger agreement, an “Altair material adverse effect” means any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence that, individually or in the aggregate, has had or would reasonably be expected to have a material adverse effect on the condition (financial or otherwise), assets, business or results of operations of Altair and its subsidiaries, taken as a whole, excluding any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence to the extent arising out of or resulting from:

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except, with respect to bullets one, two, three, four and five above, to the extent that such change, effect, development, circumstance, condition, fact, state of facts, event or occurrence is disproportionately adverse to Altair and its subsidiaries relative to others in the industry or industries in which Altair and its subsidiaries operate, in which case only the incremental disproportionate adverse change, effect, development, circumstance, condition, fact, state of facts, event or occurrence may be taken into account in determining whether a material adverse effect has occurred or would reasonably be expected to occur.

Certain of Siemens Industry’s representations and warranties in the merger agreement are qualified by a “Siemens Industry material adverse effect” standard (that is, it will not be deemed to be untrue or incorrect unless its failure to be true or correct has had or would reasonably be expected to have, individually or in the aggregate, a Siemens Industry material adverse effect). A “Siemens Industry material adverse effect” means any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence that that would reasonably be expected to prevent, impair or materially delay the ability of Siemens Industry or Merger Sub to perform its obligations under the merger agreement or consummate the merger or the other transactions contemplated thereby.

Conduct of Businesses of Altair Prior to Completion of the Merger

The merger agreement provides for certain restrictions on Altair’s and its subsidiaries’ activities until the effective time. In general, except as required or expressly contemplated by the merger agreement, as required by applicable law or as consented to in writing by Siemens Industry (which may not be unreasonably withheld, conditioned or delayed), subject to specified exceptions set forth in the merger agreement and the disclosure schedules thereto, Altair will, and will cause its subsidiaries to, use reasonable best efforts to conduct its business in accordance with applicable law and in the ordinary course of business.

In addition, except as required or expressly contemplated by the merger agreement, as required by applicable law or as consented to in writing by Siemens Industry (which may not be unreasonably withheld,

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conditioned or delayed), subject to specified exceptions set forth in the merger agreement and the disclosure schedules thereto, Altair will not, and will cause its subsidiaries not to:

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Conduct of Businesses of Siemens Industry Prior to Completion of the Merger

The merger agreement also provides for certain restrictions on Siemens Industry’s activities until the effective time. In general, Siemens Industry will not, and will cause its affiliates not to, take any action that is intended to, or would reasonably be expected to, individually or in the aggregate, prevent, materially delay or materially impede the ability of Siemens Industry and Merger Sub to consummate the merger or the other transactions contemplated by the merger agreement, including the financing thereof.

Special Meeting and Board Recommendation

Altair must cause the proxy statement to be filed with the SEC in definitive form and mailed to Altair’s stockholders as promptly as reasonably practicable following the later of (x) the end of the ten-day waiting period under Rule 14a-6(a) under the Exchange Act (or the earlier date on which the SEC confirms it will not review this proxy statement) and (y) the date on which the SEC confirms that it has no further comments on the proxy statement. As soon as reasonably practicable following the commencement of the mailing of the proxy statement, and in any event no later than 45 days thereafter, Altair must convene and hold a meeting of the Altair stockholders for purposes of submitting the merger agreement proposal to its stockholders for adoption. The special meeting constitutes that required meeting of the Altair stockholders.

Subject to the ability of the Altair board of directors to make an adverse recommendation change, the Altair board of directors is required to recommend to Altair stockholders the adoption of the merger agreement, and

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Altair is required to include that recommendation in this proxy statement and use reasonable best efforts to obtain from Altair stockholders the approval of the merger agreement proposal.

Under the terms of the merger agreement, Altair may adjourn or postpone the Altair special meeting (i) with the consent of Siemens Industry or (ii) with prior notice to Siemens Industry, to the extent Altair believes in good faith that such adjournment or postponement is reasonably necessary (a) to ensure that any required supplement or amendment to the proxy statement is provided to holders of shares of Altair common stock within a reasonable amount of time in advance of the meeting, (b) to allow reasonable additional time to solicit additional proxies necessary to obtain the Altair stockholder approval, (c) to ensure there are sufficient shares of Altair common stock represented and voting to constitute a quorum necessary to conduct the business of the special meeting or (d) otherwise where required to comply with applicable law. However, Altair may not adjourn or postpone the special meeting more than ten business days in connection with any one adjournment or postponement or, solely with respect to the foregoing clauses (b) and (c), more than an aggregate of 30 days from the original date of the special meeting, in each case without the prior written consent of Siemens Industry. In addition, Altair may not adjourn or postpone the special meeting more than two business days prior to the date on which the special meeting is scheduled to occur, in the case of an adjournment under clauses (b) or (c).

Unless the merger agreement is terminated in accordance with its terms, Altair must submit the merger agreement to its stockholders for adoption at the special meeting even if the Altair board of directors has made an adverse recommendation change or there has been an announcement or disclosure of or communication to Altair of any acquisition proposal.

No Shop; Restrictions on Solicitation of Acquisition Proposals

Under the terms of the merger agreement, subject to certain exceptions described below, Altair has agreed that, from and after October 30, 2024 until the earlier to occur of the termination of the merger agreement and the effective time, Altair will not, will cause its subsidiaries not to, and will use reasonable best efforts to cause its and their respective directors, officers and employees and direct its and their other representatives not to, directly or indirectly:

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The foregoing restrictions do not prohibit Altair or any of its subsidiaries from amending, modifying or granting any waiver or release under any standstill, confidentiality or similar agreement of Altair or its subsidiaries, in each case, solely to the extent the Altair board of directors determines, in consultation with its outside legal counsel, that the failure to do so would be reasonably likely to be inconsistent with its fiduciary duties under applicable law.

In addition, under the merger agreement, Altair has agreed that it will, and will cause its subsidiaries and its and their respective directors, officers and employees, and will direct its other representatives to, cease immediately and cause to be terminated any and all existing activities, discussions, negotiations or solicitations of acquisition proposals, if any, with any third party and its representatives conducted prior to October 30, 2024 with respect to any acquisition proposal. Altair also agreed to, and did, within three business days after October 30, 2024, (i) request in writing that each person that had previously executed a confidentiality agreement in connection with its consideration of an acquisition proposal or any inquiry or proposal that constitutes, or would reasonably be expected to lead to, any acquisition proposal promptly destroy or return to Altair all nonpublic information previously furnished by Altair or any of its representatives to such person or any of its representatives in accordance with the terms of such confidentiality agreement and (ii) terminate access to any physical or electronic data rooms relating to a possible acquisition proposal by such person and its representatives.

Notwithstanding the prohibitions described above, if, prior to Altair stockholders’ adopting the merger agreement, Altair receives an acquisition proposal from a third party that did not result from a breach of Altair’s non-solicitation obligations and the Altair board of directors determines in good faith, after consultation with its outside legal counsel and financial advisors, that (i) such acquisition proposal constitutes or would reasonably be expected to lead to a superior proposal and (ii) failure to engage in negotiations or discussions with such third party would be inconsistent with its fiduciary duties under applicable law, Altair may (i) engage in negotiations or discussions with such third party and its representatives and (ii) furnish to such third party or its representatives nonpublic information relating to Altair or any of its subsidiaries and afford access to the business, properties, assets, books or records and personnel of Altair or any of its subsidiaries pursuant to an acceptable confidentiality agreement, provided that Altair also provides Siemens Industry the same such nonpublic information (to the extent not previously provided to Siemens Industry) substantially concurrently with providing it to the third party and any competitively sensitive information or data provided to such third party who is, or whose affiliates include, a competitor, supplier or customer of Altair or any of its subsidiaries will be provided in a separate “clean data room” and subject to customary “clean team” arrangements regarding access to such information or data.

Altair is obligated to notify Siemens Industry promptly (and in any event within 24 hours) of any receipt by Altair of any acquisition proposal and any material amendment or modification to the material terms of any previously received acquisition proposal. The notice must include the identity of the person making such acquisition proposal and unredacted copies of all portions of the acquisition proposal and all related documents, in each case that contain material terms and conditions thereof, and if such acquisition proposal or any portion thereof was not provided in writing, a summary of the material terms and conditions thereof. Altair must also notify Siemens Industry promptly (and in any event within 24 hours) of any request for nonpublic information relating to Altair or any of its subsidiaries or for access to the business, properties, assets, books or records or

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personnel of Altair or any of its subsidiaries by any third party that has notified Altair that it is considering making, or has made, an acquisition proposal.

Altair must keep Siemens Industry reasonably informed on a reasonably prompt basis of the status of material discussions or negotiations and material terms and conditions of any acquisition proposal and any material developments related thereto, including promptly (but in no event later than 24 hours after receipt) providing Siemens Industry unredacted copies of all material portions of any correspondence and written materials (including any amendments or modifications thereto) that describe such material terms and conditions and summaries of all material oral communications between Altair or any of its subsidiaries or any of their representatives, on the one hand, and the potential counterparty and any of its representatives, on the other hand, in connection therewith.

An “acquisition proposal” for purposes of the merger agreement means any offer or proposal from any third party relating to, in a single transaction or a series of related transactions:

A “superior proposal” for purposes of the merger agreement means a bona fide unsolicited written acquisition proposal (but substituting “50%” for all references to “20%” in the definition of acquisition proposal) that the Altair board of directors determines in good faith, after consultation with its outside legal counsel and financial advisors, is more favorable from a financial point of view to Altair stockholders (in their capacity as such) than the merger, in each case, taking into consideration:

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Change of Recommendation; Match Rights

The merger agreement requires the Altair board of directors to recommend that Altair stockholders adopt the merger agreement and the transactions contemplated thereby and not make an adverse recommendation change as described above. Notwithstanding the foregoing, prior to Altair stockholders adopting the merger agreement, the Altair board of directors may:

Notwithstanding the foregoing, prior to making an adverse recommendation change, Altair must provide Siemens Industry four business days’ prior written notice advising Siemens Industry that it intends to take such action. The notice must specify the reasons for the adverse recommendation change and (i) in the case of a superior proposal, includes the identity of the person or group making such acquisition proposal, the terms thereof and attaches a copy of all proposed agreements for such superior proposal and other documents and information described above under the section titled “—No Shop; Restrictions on Solicitation of Acquisition Proposals” or (ii) in the case of an intervening event, a reasonably detailed description of the facts and circumstances relating to such intervening event. Altair must also, and must cause its directors, officers and employees and direct all of its other representatives to, negotiate with Siemens Industry in good faith (to the extent Siemens Industry wishes to negotiate) during such four business day period prior to making an adverse recommendation change to make such adjustments to the terms and conditions of the merger agreement as Siemens Industry may propose, and after such notice period, the Altair board of directors has considered in good faith any revisions to the terms of the merger agreement proposed in writing by Siemens Industry that, if accepted by Altair, would be binding upon Siemens Industry, and has determined in good faith, after consultation with its outside legal counsel and financial advisors, that any such revisions have not obviated the need to effect the adverse recommendation change or, in the case of a superior proposal, that such acquisition proposal continues to constitute a superior proposal before making such adverse recommendation change. With respect to any adverse recommendation change in response to a superior proposal, if there is any change to the financial terms or any other material terms of the then-existing superior proposal (including the form, amount or timing of payment of consideration proposed to be received by Altair stockholders as a result of such superior proposal or any substantive change in the terms relating to conditionality, termination or termination fees, with regulatory efforts and financing deemed to be material terms), Altair must again comply with the obligations described in clause (i) of this paragraph, except the four business day period will be replaced with a two business day period.

An “intervening event” for purposes of the merger agreement is any event, fact, circumstance, development or occurrence that:

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provided that in no event will any of the following constitute or be deemed an intervening event: (i) the receipt, existence or terms of an acquisition proposal or any matter relating thereto or the consequences thereof, (ii) any change in the price or trading value of shares of Altair common stock or other securities of Altair, (iii) the fact, in and of itself, that Altair exceeds earnings projections or predictions or results of operations made by Altair or securities or financial analysts or any resulting analyst upgrades of Altair securities and (iv) any effect to the extent resulting from any breach of the merger agreement by Altair (provided that, in the case of the foregoing clauses (ii) and (iii), the underlying causes of such effect may be considered and taken into account in determining whether there has been an intervening event).

In addition, nothing in the merger agreement prohibits Altair or the Altair board of directors from (i) taking and disclosing to Altair stockholders a position contemplated by Rule 14d-9 and Rule 14e-2(a) promulgated under the Exchange Act (or any similar communication to stockholders in connection with the making or amendment of a tender offer or exchange offer) or from making any legally required disclosure to stockholders with regard to the transactions contemplated by the merger agreement or an acquisition proposal (provided that neither Altair nor the Altair board of directors may make an adverse recommendation change unless permitted by the merger agreement), (ii) issuing a “stop, look and listen” disclosure or similar communication of the type contemplated by Rule 14d-9(f) under the Exchange Act or (iii) contacting and engaging in discussions with any person or group and their respective representatives who has made an offer, inquiry, proposal or indication of interest with respect to an acquisition proposal that was not solicited in breach of the merger agreement solely for the purpose of clarifying the terms of such offer or informing such third party of the non-solicitation restrictions imposed by the merger agreement.

Regulatory Clearances and Approvals Required for the Merger

The completion of the merger is conditioned on, among other things, the required regulatory approvals having been obtained or received (or, as applicable, the waiting periods with respect thereto having expired or been terminated), including the expiration or termination of any applicable waiting period under the HSR Act.

Subject to the terms and conditions of the merger agreement, each of Altair and Siemens Industry has agreed to take, or cause to be taken (including by causing their affiliates to take), all actions and to do, or cause to be done, all things necessary, proper or advisable under applicable law to consummate the transactions contemplated by the merger agreement as promptly as practicable, including (i) preparing and filing as promptly as practicable with any governmental authority or other third party all documentation to effect all necessary, proper or advisable filings, notices, petitions, statements, registrations, submissions of information, applications and other documents and (ii) obtaining and maintaining all approvals, consents, registrations, permits, authorizations and other confirmations required to be obtained from any governmental authority or other third party that are necessary, proper or advisable to consummate the merger, including the required regulatory approvals, as promptly as practicable (and in any event, prior to the end date or the extended end date, as applicable).

The merger cannot be completed until all applicable waiting periods (and any extensions thereof) under the HSR Act relating to the merger, and any commitment to, or agreement with, any governmental authority to delay the consummation of, or not to consummate before a certain date, the merger, have expired or been terminated, and other required regulatory approvals have been obtained or received or, as applicable, the waiting periods with respect thereto have expired or been terminated. There can be no assurance that a challenge to the merger on regulatory grounds by a governmental authority or private party will not be made or, if such a challenge is made, that it would not be successful.

Each of Altair and Siemens Industry has agreed to (x) furnish to the other, as promptly as practicable, all information within its (or its affiliates’) control requested by such other party and required for such other party to make any application or other filing to be made by it pursuant to any applicable law in connection with the merger, (y) keep each other reasonably apprised of the status of, and work cooperatively in connection with

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obtaining, the required regulatory approvals and any other consents, clearances, registrations, approvals, permits, waivers, expirations or terminations of waiting periods and authorizations pursuant to any competition laws from any governmental authority in connection with the merger and (z) respond as promptly as practicable to any inquiries received from any governmental authority for additional information or documentary material that may be requested pursuant to the HSR Act or any other applicable competition laws.

If any objections are asserted with respect to the transactions contemplated by the merger agreement under the HSR Act, any other applicable competition law or in connection with any required regulatory approval, or if any proceeding under competition laws is instituted or threatened by any governmental authority challenging any of the transactions contemplated by the merger agreement, Siemens Industry and Altair have agreed to use reasonable best efforts to resolve such objections as promptly as practicable.

Each of Altair and Siemens Industry has agreed to oppose (1) any administrative or judicial proceeding that is initiated or threatened to be initiated challenging the merger agreement or the consummation of the transactions contemplated thereby as violative of any competition law (including seeking to have any stay or temporary restraining order entered by any court or other governmental authority vacated or reversed) and (2) any request for the entry of, and to seek to have vacated or terminated, any order in connection with any competition law that would reasonably be expected to restrain, prevent or materially delay the consummation of the transactions contemplated by the merger agreement, including in the case of either (1) or (2), by defending through litigation any proceeding brought by any governmental authority pursuant to any competition law, and vigorously pursuing all available avenues of administrative and judicial appeal. However, in no event will Siemens Industry or its subsidiaries or affiliates be required to take any remedy action, except to the extent that such remedy action would not, and would not reasonably be expected to, individually or in the aggregate, result in a burdensome condition. The reasonable best efforts of Siemens Industry will include taking any remedy action that would not, and would not reasonably be expected to, individually or in the aggregate, result in a burdensome condition.

Altair has agreed not to, and has agreed to cause its subsidiaries not to, offer, propose, negotiate, agree to, commit to, effect or take any remedy action without the prior written consent of Siemens Industry, and Altair has agreed to, and has agreed to cause its subsidiaries to, offer, propose, negotiate, agree to, commit to, effect and take any remedy action if so directed by Siemens Industry in connection with obtaining the required regulatory approvals; provided, that any remedy action is conditioned on the closing of the merger. If requested by Siemens Industry, Altair must divest, hold separate or take or commit to take any action that limits its freedom of action with respect to, or its ability to retain, any of the businesses, services or assets of Altair or its subsidiaries, provided that any such action is conditioned on the consummation of the merger and the other transactions contemplated by the merger agreement.

Neither Altair nor Siemens Industry will take any action if such action would (1) make it materially more likely that there would arise any impediments under any competition law or other applicable law that may be asserted by the FTC, the Antitrust Division, any State Attorney General or any other governmental authority to the consummation of the merger and the other transactions contemplated by the merger agreement, as promptly as practicable, or (2) impose any material delay in the expiration of any waiting period or obtaining of any approval from any governmental authority necessary to consummate the transactions contemplated by the merger agreement.

Each of Altair and Siemens Industry will (i) promptly notify the other party of any substantive communication to that party from the FTC, the Antitrust Division, any State Attorney General or any other governmental authority and, subject to applicable law, permit the other to review, reasonably in advance, any written communication or presentation proposed to be submitted to any governmental authority and consider in good faith any comments such other party may provide, (ii) not agree to participate in any substantive meeting or discussion with any governmental authority in respect of any filings, investigation or inquiry concerning any competition or antitrust matters in connection with the merger agreement or the merger and the other transactions

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contemplated by the merger agreement, unless it consults with the other party in advance and, to the extent permitted by such governmental authority, gives the other party the opportunity to attend and participate thereat and (iii) furnish the other party with copies of all filings (other than HSR filings) and material correspondences and communications between them and their affiliates and their respective representatives on the one hand, and any governmental authority or members or their respective staffs on the other hand, with respect to any competition laws in connection with the merger agreement.

Siemens Industry has the sole right to direct all matters with any governmental authority related to, and to control and lead all actions, communications, decisions and strategy for obtaining the required regulatory approvals and any other consents, clearances, registrations, approvals, permits, waivers, expirations or terminations of waiting periods and authorizations pursuant to any competition laws from any governmental authority, in connection with the transactions contemplated by the merger agreement, provided that Siemens Industry will consult in good faith with Altair and its representatives with respect to strategy and substantive communications regarding such matters, including any litigation under any competition laws. Siemens Industry also has the right to commit to or agree with any governmental authority to stay any applicable waiting period under the HSR Act or any other applicable competition law if such commitment is reasonably designed to obtain all required regulatory approvals as promptly as reasonably practicable and if Siemens Industry’s outside legal counsel advises that such commitment is advisable, provided that Siemens Industry will consult with Altair in good faith prior to making any such commitment, and Siemens Industry will not agree to stay, toll or extend any waiting period under competition law or to delay the consummation of, or to not consummate before a certain date, the merger, if such commitment would reasonably be expected to delay the consummation of the merger beyond the extended end date.

On November 15, 2024, each of Altair and Siemens Industry filed a notification of the proposed merger with the FTC and the Antitrust Division under the HSR Act. The waiting period expired on December 16, 2024 at 11:59 p.m., Eastern Time.

In addition, Altair and Siemens Industry will prepare and, at least 65 days prior to the closing date, file with the DDTC, in accordance with ITAR at 22 C.F.R. 122.4(b), a notification regarding the merger and the other transactions contemplated in the merger agreement.

Although the parties expect that the required regulatory approvals will be obtained, the parties cannot assure you that such approvals will be timely obtained or obtained at all or that the granting of regulatory approvals will not involve the imposition of additional conditions on the completion of the merger, or a commitment or agreement to take remedial actions, including divesting assets or businesses, creating, modifying or transferring contractual rights or obligations or entering into supply or services agreements. Any such requirements could result in the conditions to the merger not being satisfied.

Employee Matters

For 12 months following the effective time, Siemens Industry will cause each Altair employee as of immediately prior to the effective time whose employment continues with Siemens Industry or one of its affiliates following such time (each, a “continuing employee”) to receive (i) an annual rate of salary or hourly wage rate, as applicable, that is no less favorable than the annual rate of salary or hourly wage rate, as applicable, provided to such continuing employee as of immediately prior to the effective time, (ii) target cash incentive opportunities that are no less favorable in the aggregate than the target cash incentive opportunities provided to such continuing employee as of immediately prior to the effective time and (iii) severance payments and benefits no less than (A) with respect to U.S.-based continuing employees, the existing Altair severance agreements and policies described in the disclosure schedules and (B) with respect to non-U.S.-based continuing employees covered by a local severance policy or statutory or regulatory severance or termination benefits, the greater of (x) those payable pursuant to the applicable local Altair severance policy disclosed in the disclosure schedules

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and (y) statutory severance or as otherwise required by applicable law, and (iv) health, welfare and retirement benefits that are substantially comparable in the aggregate to health, welfare and retirement benefits provided, as determined by Siemens Industry in its sole discretion, either (A) to such continuing employee as of immediately prior to the effective time or (B) to similarly situated employees of Siemens Industry (including paid time off, but excluding any defined benefit pension, retiree medical or life insurance benefits, equity and equity-based incentives and retention, change in control or similar plans, policies or agreements).

To the extent the short-term incentive bonuses for the performance period in which the effective time occurs (or the immediately preceding performance period) remain unpaid as of the closing of the merger, Siemens Industry will pay or cause one of its affiliates to pay bonuses provided for under the Altair short-term performance bonus programs for the performance period in which the effective time occurs (or if applicable, the immediately preceding performance period) to each continuing employee, with the amount being determined based on actual performance either (i) if the closing occurs on or before December 31, 2025, through the last day of the applicable performance period (but in no event later than December 31, 2025) or (ii) if the closing occurs after December 31, 2025, through the earlier of (x) the last day of the applicable performance period or (y) the last day of the surviving corporation’s fiscal year, as such fiscal year may be modified following the closing, and further subject to and conditioned upon such continuing employee satisfying any continued employment and other requirements applicable to such short-term performance bonus program; provided, that, in the event of an involuntary termination of employment of a continuing employee without “cause” by the surviving corporation following the effective time (as determined by the surviving corporation) and prior to the date the bonuses are paid, the continuing employee will, subject to such continuing employee’s timely execution of a release of claims in a form prescribed by the surviving corporation, be entitled to receive the bonuses as if such continuing employee had remained employed through the payment date, pro-rated to reflect such continuing employee’s actual tenure during the applicable performance period. The bonuses will be paid by Siemens Industry or its affiliate at the time or times that they would normally be paid by Altair but in all events within 60 days following the end of the applicable performance period in accordance with the terms and conditions applicable thereto.

Following the effective time, Siemens Industry will cause the surviving corporation and any of its respective subsidiaries to use commercially reasonable efforts to (i) waive all limitations as to any pre-existing condition or waiting periods with respect to participation and coverage requirements applicable to each continuing employee under any employee benefit plan maintained by Siemens Industry or its affiliates in which such continuing employees become eligible to participate (such plan, a “Siemens Industry benefit plan”), (ii) credit each continuing employee, as of and after the effective time, for any copayments, deductibles, offsets or similar payments made during the plan year that includes the effective time for purposes of satisfying any applicable copayment, deductible, offset or similar requirements under the comparable Siemens Industry benefit plan and (iii) give all continuing employees full credit for such continuing employees’ service for purposes of eligibility, vesting and accruals under any Siemens Industry benefit plan to the same extent and for the same purpose that such service was credited for under any similar Altair benefit plan immediately prior to the effective time.

Directors’ and Officers’ Indemnification and Insurance

Under the merger agreement, for a period of six years after the effective time, Siemens Industry must cause the surviving corporation to indemnify and hold harmless to the fullest extent permitted by applicable law and the organizational documents of Altair or its subsidiaries, the present and former directors, officers and agents of Altair and its subsidiaries and any individuals serving in such capacity at or with respect to other persons at Altair’s or its subsidiaries’ request from and against any losses, damages, liabilities, costs, expenses (including attorneys’ fees), judgments, fines, penalties and amounts paid in settlement (including all interest, assessments and other charges paid or payable in connection with or in respect of any thereof) in respect of the persons having served in such capacity prior to the effective time.

In addition, for a period of six years following the effective time, Siemens Industry is required to maintain in effect provisions in the organizational documents of the surviving corporation and its subsidiaries regarding

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elimination of liability of directors, indemnification of directors, officers and agents and advancement of fees, costs and expenses that are no less advantageous to the intended beneficiaries than the corresponding provisions that were in existence as of October 30, 2024.

From and after the effective time, Siemens Industry is required to cause the surviving corporation and its subsidiaries to honor and comply with their respective obligations under any indemnification agreement with any director or officer of Altair or its subsidiaries, and not amend, repeal or otherwise modify any such agreement in any manner that would adversely affect any rights of such persons.

Prior to the effective time of the merger, Altair will (or if Altair is unable to, Siemens Industry will cause the surviving corporation to) purchase a directors’ and officers’ liability insurance and fiduciary liability insurance “tail” policy for a period of six years after the effective time with respect to matters arising at or prior to the effective time with terms, conditions, retentions and limits of liability that are no less favorable than the coverage provided under Altair’s existing policies as of October 30, 2024, with a one-time cost not in excess of 350% of the last aggregate annual premium paid by Altair for its directors’ and officers’ liability insurance and fiduciary liability insurance prior to October 30, 2024, and if the cost of such “tail” insurance policy would otherwise exceed such amount, the surviving corporation must purchase a policy with the greatest coverage available for a cost not exceeding such amount.

Treatment of Certain Indebtedness

In connection with the merger, Altair is required to repay the loans outstanding, if any, and terminate all commitments available under the Third Amended and Restated Credit Agreement, dated as of October 18, 2017, by and among Altair, JPMorgan Chase Bank, N.A., as administrative agent, sole bookrunner and sole lead arranger, and the lenders parties thereto (as amended, restated, supplemented or otherwise modified from time to time, the “credit agreement”). The merger agreement provides that Altair will use commercially reasonable efforts to obtain and provide to Siemens Industry, at least two business days prior to the closing date, a customary payoff letter setting forth all amounts necessary to be paid as of the closing date in order to repay in full all the obligations thereunder and providing for the guarantees and liens in respect of the credit agreement to be released, together with any necessary UCC authorizations or other releases as are required or as Siemens Industry may reasonably request to evidence the satisfaction and discharge in full of such obligations at the closing, and the release of all liens with respect thereto effective at the closing.

In addition, the merger agreement provides that, on the closing date, Siemens Industry, Merger Sub and Altair will, as and to the extent required by the Indenture, dated as of June 14, 2022, by and between Altair, as issuer, and U.S. Bank Trust Company, National Association, as trustee, governing the 1.750% convertible notes due 2027 (the “convertible notes indenture” and the notes thereunder, the “convertible notes”), execute, and use reasonable best efforts to cause the trustee to execute, any supplemental indenture required by the convertible notes indenture and deliver any certificates and other documents required by the convertible notes indenture to be delivered by such persons in connection with such supplemental indenture. Prior to the effective time, Altair must give any notices and take all actions required under, and with the prior consent of Siemens Industry, not to be unreasonably withheld, conditioned or delayed, may take actions permitted under, the terms of the convertible notes, the convertible notes indenture or applicable law, and must take any other actions reasonably requested by Siemens Industry to the extent such actions are permitted or contemplated by the terms of the convertible notes, convertible notes indenture or applicable law (with respect to the convertible notes indenture or the convertible notes) in connection with the merger and the other transactions contemplated in the merger agreement. Altair expects, though cannot guarantee, that the holders of the convertible notes will elect to convert their convertible notes in connection with the closing of the merger under the provisions of the convertible notes indenture that address make whole fundamental change of Altair.

The foregoing description of the convertible notes indenture and the rights of holders of the convertible notes thereunder are summaries only and are qualified in their entirety by reference to the convertible notes indenture.

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This proxy statement does not constitute an offer to sell or the solicitation of an offer to buy, or a notice to redeem, any debt securities of Altair. It does not constitute a prospectus or prospectus equivalent document for any such securities.

Other Covenants

The merger agreement contains additional agreements of Siemens Industry, Altair and Merger Sub relating to, among other things:

Conditions to the Merger

The respective obligations of each party to consummate the merger are subject to the satisfaction or waiver of the following conditions:

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The obligations of Siemens Industry and Merger Sub to consummate the merger are subject to the satisfaction or waiver of the following additional conditions:

The obligation of Altair to consummate the merger is subject to the satisfaction or waiver of the following additional conditions:

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Termination of the Merger Agreement

Termination by Siemens Industry or Altair

The merger agreement may be terminated and the merger may be abandoned at any time prior to the effective time (notwithstanding any approval of the merger agreement by Altair stockholders):

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Termination by Altair

The merger agreement may be terminated at any time prior the effective time by Altair if:

Termination by Siemens Industry

The merger agreement may be terminated at any time prior to the effective time by Siemens Industry if:

Termination Fees and Expenses

Altair Termination Fee

The merger agreement provides that Altair will pay Siemens Industry a termination fee of $372 million if: