144 0001908962 XXXXXXXX LIVE 0000860413 First Interstate BancSystem, Inc. 001-34653 401 North 31st Street Billings MT 59101 1-406-255-5311 Jonathan R. Scott Trust dtd 11/13/2004 Former Director Common Goldman Sachs & Co. LLC 200 West Street New York NY 10282 66396 2356394.04 97376026 04/30/2026 NASD Common 06/20/2020 Gift Scott Family Member Y 11/03/1993 52991 06/20/2020 None Common 06/01/2024 Acquired as compensation -- Restricted Stock Units Issuer N 3401 06/01/2024 Compensation Common 06/01/2024 Acquired as compensation -- Restricted Stock Units Issuer N 1133 06/01/2024 Compensation Common 06/01/2025 Acquired as compensation -- Restricted Stock Units Issuer N 3014 06/01/2025 Compensation Common 06/01/2025 Acquired as compensation -- Restricted Stock Units Issuer N 565 06/01/2025 Compensation Common 06/01/2020 Acquired as compensation -- Restricted Stock Units Issuer N 2080 06/01/2020 Compensation Common 03/15/2020 Acquired as a gift Scott Family Memeber Y 02/15/1972 1000 03/15/2020 None Common 06/01/2018 Acquired as compensation -- Restricted Stock Units Issuer N 859 06/01/2018 Compensation Common 06/01/2022 Acquired as compensation -- Restricted Stock Awards Issuer N 513 06/01/2022 Compensation Common 11/03/1983 Acquired as a gift Scott Family Member Y 02/15/1972 840 11/03/1983 None N Jonathan R. Scott Trust dtd 11/13/2004 401 North 31st Street Billings MT 59101 Common 03/26/2026 3000 100348.2 04/30/2026 Goldman Sachs & Co. LLC on behalf of Jonathan R. Scott Trust dtd 11/13/2004