Sec Form 5 Filing - Scott Jeremy @ FIRST INTERSTATE BANCSYSTEM INC - 2024-12-31

FORM 5 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Scott Jeremy 2. Issuer Name and Ticker or Trading Symbol FIRST INTERSTATE BANCSYSTEM INC [ FIBK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 859 MAIN STREET, 3. Date of Earliest Transaction (MM/DD/YY) 12/31/2024 (Street) DAYTON, WY82836 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 2,946 ( 1 ) D Common Stock 3,488,355 ( 2 ) I See footnote ( 2 ) ( 5 ) Common Stock 12/05/2024 G V 475 A $ 0 3,488,830 ( 3 ) I See footnote ( 3 ) ( 5 ) Common Stock 12/05/2024 G V 475 A $ 0 3,489,305 ( 4 ) I See footnote ( 4 ) ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Scott Jeremy 859 MAIN STREET DAYTON, WY82836 X X Jeremy Scott TTEE, Jeremy Scott Revocable Trust Dtd 6/25/15 859 MAIN STREET BOX 592 DAYTON, WY82836 X NBAR5 Limited Partnership PO BOX 7113 BILLINGS,, MT59103 X Signatures JEREMY SCOTT, By: /s/ Timothy Leuthold, Attorney-in-Fact for Reporting Person 07/18/2025 Signature of Reporting Person Date JEREMY SCOTT TTEE, JEREMY SCOTT REVOCABLE TRUST DTD 6/25/15, By: /s/ Timothy Leuthold, Attorney-in-Fact 07/18/2025 Signature of Reporting Person Date NBAR5 LIMITED PARTNERSHIP, By: /s/ Timothy Leuthold, Attorney-in-Fact 07/18/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares issuable upon vesting of restricted stock units held as of the date of this filing and granted to Jeremy Scott pursuant to the issuer's 2023 Equity and Incentive Plan pursuant to the issuer's director compensation policy for service as an issuer director. The restricted stock units vest on June 1, 2026, subject to Mr. Scott's provision of continuous service to the issuer through the earlier of the applicable vesting date or the date of the issuer's 2026 annual meeting of stockholders. ( 2 )Composed of 69,892 shares held of record by Jeremy Scott TTEE, Jeremy Scott Revocable Trust Dtd 6/25/15; 3,416,108 shares held of record by NBAR5 Limited Partnership; and 2,355 shares held of record by Jeremy Scott's spouse that were inadvertently omitted from Mr. Scott's Form 3 filed on February 11, 2022, that corresponded with his joining of the Scott family Schedule 13D shareholder group. ( 3 )Includes these 475 shares received by Jeremy Scott's spouse as a gift from a family member. ( 4 )Includes these 475 shares received by Jeremy Scott TTEE, Jeremy Scott Revocable Trust Dtd 6/25/15 as a gift from a family member. ( 5 )As a result of agreements entered into among the reporting persons, the issuer, and other stockholders of the issuer signatory thereto, the reporting persons may be deemed members of a group with the other signatories to the agreement and may be deemed to share beneficial ownership of the securities reported herein. Each of the reporting persons disclaims beneficial ownership of any such securities, except to the extent of his or its pecuniary interest therein. The reporting persons expect to file future Forms 4 or 5, if any, together with the indication of direct or indirect ownership in Tables I and II being made from Jeremy Scott's perspective, unless expressly noted otherwise by footnote. The nature of beneficial ownership is described in detail by footnote for all reporting persons.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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