X0306 4 2022-07-14 0001701732 Altair Engineering Inc. ALTR 0001839690 Buckner Stephanie C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 Chief Operating Officer Class A Common Stock 2022-07-14 4 A 0 143 41.68 A 9806 D Class A Common Stock 5750 I By husband Shares purchased under the Altair Engineering Inc. 2021 Employee Stock Purchase Plan in a transaction exempt under Rule 16b-3(c). Includes 4,475 Class A Common Stock restricted stock units that are unvested. Includes 3,411 Class A Common Stock restricted stock units that are unvested. /s/ Raoul Maitra, attorney-in-fact for Stephanie Bucker 2022-07-18