X0306 4 2021-09-24 0001701732 Altair Engineering Inc. ALTR 0001720809 Christ Revocable Trust C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 Class A Common Stock 2021-09-24 4 C 0 374950 0 A 374950 D Class A Common Stock 2021-09-24 5 G 0 E 187475 0 D 187475 D Class A Common Stock 2021-09-24 5 G 0 E 187475 0 D 0 D Class B Common Stock 0 2021-09-24 4 C 0 374950 0 D Class A Common Stock 374950 5881778 D On September 24, 2021, the reporting person transferred 187,475 shares of Class A common stock to a family trust of which the Trustee of the reporting person serves as co-Trustee. A member of the Trustee's immediate family is the sole beneficiary of the trust. Each share of Class B common stock is immediately convertible, at the option of the shareholder, 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 Altair Engineering Inc. Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-225412) for a description of the conversion rights. /s/ Raoul Maitra, attorney-in-fact for Christ Revocable Trust dated May 8, 2015 2021-09-27