X0306 4/A 2022-07-14 2022-07-18 0 0001701732 Altair Engineering Inc. ALTR 0001912935 Marraccini Jeffrey C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER ROAD TROY MI 48083 0 1 0 0 See Remarks Class A Common Stock 2022-07-14 4 A 0 145 41.68 A 2399 D Shares purchased under the Altair Engineering Inc. 2021 Employee Stock Purchase Plan in a transaction exempt under Rule 16b-3(c). Includes 1,502 Class A Common Stock restricted stock units that are unvested. This amendment is being filed to correct the number of securities beneficially owned following the reported transaction. The number of securities beneficially owned was misstated on the Reporting Person's original Form 4 filed with the Securities and Exchange Commission on July 18, 2022. Chief Information Security Officer /s/ Raoul Maitra, attorney-in-fact for Jeffrey Marraccini 2022-07-18