X0306 4 2021-12-09 0001701732 Altair Engineering Inc. ALTR 0001892309 Carter Sandra Ann C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 Class A Common Stock 2021-12-09 4 A 0 2756 0 A 2756 D Class A Common Stock 2021-12-09 4 A 0 1378 0 A 4134 D On December 9, 2021, the Reporting Person was granted 2,756 Class A Common Stock restricted stock units, which vest in 3 equal annual installments commencing December 9, 2022. Each restricted stock unit represents a contingent right to receive one share of Class A Common Stock. Includes 2,756 Class A Common Stock restricted stock units that are unvested. On December 9, 2021, the Reporting Person was granted 1,378 Class A Common Stock restricted stock units, which will vest on December 9, 2022. Each restricted stock unit represents a contingent right to receive one share of Class A Common Stock. Includes 4,134 Class A Common Stock restricted stock units that are unvested. /s/ Raoul Maitra, attorney-in-fact for Sandra Ann Carter 2021-12-10