Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

  Names of Reporting Persons

  George J. Christ

  Check the Appropriate Box if a Member of a Group

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  United States

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power:

  10,525,782*

  Shared Voting Power:

  0

  Sole Dispositive Power:

  10,525,782*

  Shared Dispositive Power:

  0

  Aggregate Amount Beneficially Owned by Each Reporting Person

  10,525,782*

  Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

  ☐

  Percent of Class Represented by Amount in Row (9)

  17.2% *

  Type of Reporting Person

  IN

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 4, 2021, there were 50,789,524 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 18, 2021. George J. Christ (“Mr. Christ”) is the Trustee of the Christ Revocable Trust dated May 8, 2015 (the “Christ Trust”), and the Manager of GC Investments, LLC (the “GC LLC” and, collectively with Mr. Christ and the Christ Trust, the “Reporting Persons”). As of December 31, 2021 (the “Event Date”), the Reporting Persons may be deemed to beneficially own an aggregate of 10,525,782 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes (i) 5,581,778 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company held by the Christ Trust and (ii) 4,944,004 shares of Class B Common Stock of the Company held by the GC LLC. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Persons, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the Reporting Persons may be deemed to beneficially own 17.2% of the shares of Class A Common Stock issued and outstanding. The percentages were obtained by dividing (a) the number of shares of Class B Common Stock beneficially owned by the Reporting Persons as set forth in Row 9 by (b) the sum of (i) 50,789,524 shares of Class A Common Stock outstanding as of October 18, 2021 and (ii) the 10,525,782 shares of Class B Common Stock beneficially owned by the Reporting Persons that are convertible into Class A Common Stock.

  Names of Reporting Persons

  Christ Revocable Trust dated May 8, 2015

  Check the Appropriate Box if a Member of a Group

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  United States

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power:

  5,581,778*

  Shared Voting Power:

  0

  Sole Dispositive Power:

  5,581,778*

  Shared Dispositive Power:

  0

  Aggregate Amount Beneficially Owned by Each Reporting Person

  5,581,778*

  Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

  ☐

  Percent of Class Represented by Amount in Row (9)

  9.9% *

  Type of Reporting Person

  OO

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 4, 2021, there were 50,789,524 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 18, 2021. George J. Christ (“Mr. Christ”) is the Trustee of the Christ Revocable Trust dated May 8, 2015 (the “Christ Trust”). As of December 31, 2021 (the “Event Date”), Mr. Christ and the Christ Trust may be deemed to beneficially own an aggregate of 5,581,778 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes 5,581,778 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Persons, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, Mr. Christ and the Christ Trust may be deemed to beneficially own 9.9% of the shares of Class A Common Stock issued and outstanding. The percentages were obtained by dividing (a) the number of shares of Class B Common Stock beneficially owned by Mr. Christ and the Christ Trust as set forth in Row 9 by (b) the sum of (i) 50,789,524 shares of Class A Common Stock outstanding as of October 18, 2021 and (ii) the 5,581,778 shares of Class B Common Stock beneficially owned by Mr. Christ and the Christ Trust that are convertible into Class A Common Stock.

  Names of Reporting Persons

  GC Investments, LLC

  Check the Appropriate Box if a Member of a Group

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  United States

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power:

  4,944,004*

  Shared Voting Power:

  0

  Sole Dispositive Power:

  4,944,004*

  Shared Dispositive Power:

  0

  Aggregate Amount Beneficially Owned by Each Reporting Person

  4,944,004*

  Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

  ☐

  Percent of Class Represented by Amount in Row (9)

  8.9%

  Type of Reporting Person

  OO

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 4, 2021, there were 50,789,524 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 18, 2021. George J. Christ (“Mr. Christ”) is the Manager of GC Investments, LLC (the “GC LLC”). As of December 31, 2021 (the “Event Date”), Mr. Christ and the GC LLC may be deemed to beneficially own an aggregate of 4,944,004 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes 4,944,004 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Persons, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, Mr. Christ and the GC LLC may be deemed to beneficially own 8.9% of the shares of Class A Common Stock issued and outstanding. The percentages were obtained by dividing (a) the number of shares of Class B Common Stock beneficially owned by Mr. Christ and the GC LLC as set forth in Row 9 by (b) the sum of (i) 50,789,524 shares of Class A Common Stock outstanding as of October 18, 2021 and (ii) the 4,944,004 shares of Class B Common Stock beneficially owned by Mr. Christ and the GC LLC that are convertible into Class A Common Stock.

Name Of Issuer:

Address of Issuer’s Principal Executive Offices:

Name of Person Filing:

Address of Principal Business Office or, if None, Residence:

Citizenship:

Title of Class of Securities:

If This Statement Is Filed Pursuant to Section 240.13d-1(b) or 240.13d-2(b) or (c), check whether the Person Filing is a:

Ownership:

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

This report on Schedule 13G, is being jointly filed by (i) the Christ Trust, (ii) the GC LLC, and (iii) Mr. Christ, as the Trustee of the Christ Trust and the Manager of the GC LLC.

Ownership of Five Percent or Less of a Class

Ownership of More Than Five Percent on Behalf of Another Person

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

Identification and Classification of Members of the Group

Notice of Dissolution of Group

Certification

A power of attorney was previously filed with the Commission and is incorporated herein by reference to Exhibits 99.2, 99.3 and 99.4 to the Schedule 13G filed by George J. Christ on February 14, 2018.

Exhibit No.

Exhibit