X0306 4/A 2019-03-11 2019-03-14 0 0001701732 Altair Engineering Inc. ALTR 0001720664 Kowal Jan C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER ROAD TROY MI 48083 1 0 0 0 Class A Common Stock 2019-03-11 4 M 0 20000 3.79 A 23000 D Class A Common Stock 2019-03-12 4 S 0 8000 37.62 D 15000 D Stock Option (right to buy) 3.79 2019-03-11 4 M 0 20000 0.00 A 2015-12-15 2024-12-15 Class A Common Stock 20000 0 D On June 14, 2018, the Reporting Person was granted 3,000 Class A Common Stock restricted stock units, which vest in 4 equal annual installments commencing June 14, 2019. Each restricted stock unit represents a contingent right to receive one share of Class A Common Stock. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $37.50 to $37.70 per share, inclusive. The reporting person undertakes to provide to Altair Engineering Inc., any security holder of Altair Engineering Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. This amendment to the original Form 4 filed on March 14, 2019 is being filed to correct the exercise date and the total number of stock options for Class A Common Stock which were exercised. /s/ Raoul Maitra, attorney-in-fact for Jan Kowal 2021-04-07