[144] First Interstate BancSystem, Inc. SEC Filing

Rhea-AI Filing Summary

First Interstate BancSystem, Inc. (FIBK) Form 144 shows a proposed sale of 40,000 shares of common stock through Piper Sandler at an aggregate market value of $1,308,800.00, with an approximate sale date of 09/02/2025 on Nasdaq. The shares were acquired on 01/02/1976 as pre-IPO stock and payment was in cash.

The filing also discloses two recent sales by the Susan Scott Heyneman Trust of 55,000 shares each on 07/14/2025 and 08/01/2025, producing gross proceeds of $1,711,231.50 and $1,532,052.50 respectively. The filer certifies no undisclosed material adverse information and follows Rule 144 disclosure requirements.

Positive

• Compliance with Rule 144 disclosure demonstrated by filing details and the signer’s representation about material information
• Use of a regulated broker (Piper Sandler) for the proposed transaction adds procedural transparency

Negative

• Insider/related-party selling activity: recent trustee sales (55,000 shares on 07/14/2025 and 55,000 shares on 08/01/2025) and a planned 40,000-share sale may signal ongoing disposition of holdings
• Sizeable aggregate proceeds from recent sales (>$1.5M each) represent meaningful liquidity events by related parties

Insights

Securities Analyst

TL;DR: Insider-related sales disclosed; planned 40,000-share sale (~$1.31M) is routine disclosure but noteworthy for monitoring insider activity.

The Form 144 reports a proposed sale of 40,000 pre-IPO shares by a person whose holdings were originally acquired in 1976, routed through Piper Sandler and slated for Nasdaq on 09/02/2025 at an aggregate market value of $1,308,800. Two recent trustee sales of 55,000 shares each in July and August generated meaningful proceeds, indicating ongoing disposition activity from related parties. For investors, these are compliance disclosures rather than statements about company operations; they signal liquidity events by insiders/related trusts that may warrant monitoring for further selling patterns but do not by themselves imply operational issues.

Corporate Governance Expert

TL;DR: Filing meets Rule 144 disclosure requirements; the trustee sales and planned sale should be tracked for governance context.

The notice documents adherence to Rule 144 procedures and includes the required representation about lack of material nonpublic information. The presence of trustee sales (Susan Scott Heyneman Trust) and a planned brokered sale could reflect estate or diversification actions. From a governance perspective, the material facts presented are procedural and transparent; impact depends on scale relative to total insider holdings and any subsequent filings showing further dispositions.

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK
Filer CCC
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer

SEC File Number

Address of Issuer

Phone

Name of Person for Whose Account the Securities are To Be Sold

See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.

Relationship to Issuer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common Stock	Piper Sandler & Co Inc 350 N 5th St Ste 1000 Minneapolis MN 55401	40000	1308800.00	104856752	09/02/2025	Nasdaq

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common Stock	01/02/1976	Pre IPO Shares	NA			40000	01/02/1976	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Susan Scott Heyneman Trust C/O First Interstate Bank 401 N 31ST ST FL 1 Billings MT 59101	Common Stock	07/14/2025	55000	1711231.50
Susan Scott Heyneman Trust C/O First Interstate Bank 401 N 31ST ST FL 1 Billings MT 59101	Common Stock	08/01/2025	55000	1532052.50

144: Remarks and Signature

Remarks

Date of Notice

Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1

ATTENTION:

The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.

Signature

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

FAQ

What does the Form 144 filed for FIBK report?

The Form 144 reports a proposed sale of 40,000 shares of First Interstate BancSystem common stock valued at $1,308,800.00, planned for 09/02/2025, acquired as pre-IPO shares on 01/02/1976.

Who is the broker handling the proposed FIBK sale?

The filing lists Piper Sandler & Co. as the broker for the proposed transaction.

Has the filer or related parties recently sold FIBK shares?

Yes. The Susan Scott Heyneman Trust sold 55,000 shares on 07/14/2025 (gross proceeds $1,711,231.50) and 55,000 shares on 08/01/2025 (gross proceeds $1,532,052.50).

Were the securities acquired by the seller recently or long-held?

The 40,000 shares to be sold were acquired on 01/02/1976 as pre-IPO shares, indicating long-term ownership.

Does the filing indicate undisclosed material information about FIBK?

The signer represents they do not know of any material adverse information not publicly disclosed; no undisclosed material facts are stated in the filing.