Ameren Illinois (NYSE: AEE) issues $350M 5.625% bonds due 2055 financing

Rhea-AI Filing Summary

Ameren Illinois Company sold $350 million principal amount of its 5.625% First Mortgage Bonds due 2055, a further issuance of bonds originally issued on March 3, 2025 in the same principal amount. The bonds were offered under an effective shelf registration on Form S-3 with a related prospectus and September 15, 2025 prospectus supplement. Ameren Illinois received approximately $358.1 million in net offering proceeds before expenses from this transaction. The report also files the underwriting agreement, indenture documents, and legal opinions related to the bond offering as exhibits.

Insights

Utility capital structure analyst

Ameren Illinois adds long-term debt via a $350 million bond tap.

Ameren Illinois Company issued an additional $350 million of its 5.625% First Mortgage Bonds due 2055, matching a prior tranche issued on March 3, 2025. This extends fixed-rate funding at the subsidiary level, secured by its first mortgage framework, which is typical for regulated utilities.

The company reports net offering proceeds of about $358.1 million before expenses, indicating issuance at a premium to par. This strengthens available cash resources but also modestly increases long-term interest obligations through 2055. Overall, this is a routine financing step under an existing shelf registration rather than a change in business strategy.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

Date of report (Date of earliest event reported): September 26, 2025

Commission File Number		Exact Name of Registrant as Specified in Charter; State of Incorporation; Address and Telephone Number		IRS Employer Identification Number
1-14756		Ameren Corporation (Missouri Corporation) 1901 Chouteau Avenue St. Louis, Missouri 63103 (314) 621-3222		43-1723446
1-3672		Ameren Illinois Company (Illinois Corporation) 10 Richard Mark Way Collinsville, Illinois 62234 (618) 343-8150		37-0211380

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrants under any of the following provisions:

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.01 par value per share		AEE		New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

	Emerging growth company
Ameren Corporation	¨
Ameren Illinois Company	¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.

Ameren Corporation	¨
Ameren Illinois Company	¨

Co-Registrant CIK	0000018654
Co-Registrant Amendment Flag	false
Co-Registrant Form Type	8-K
Co-Registrant DocumentperiodEndDate	2025-09-26
Co-Registrant Written Commuunications	false
Co-Registrant Solicitating Materials	false
Co-Registrant PreCommencement Tender Offer	false
Co-Registrant PreCommencement Tender Offer	false
Co-Registrant Entity PreCommencement Issuer Tender Offer	false

ITEM 8.01 Other Events.

On September 26, 2025, Ameren Illinois Company (“Ameren Illinois”), a subsidiary of Ameren Corporation, sold $350 million principal amount of its 5.625% First Mortgage Bonds due 2055 (the “Bonds”). These Bonds are a further issuance of the 5.625% First Mortgage Bonds due 2055 previously issued on March 3, 2025, in the principal amount of $350 million. The Bonds were offered pursuant to a Registration Statement on Form S-3 (File No. 333-274977-01), which became effective on October 13, 2023, and a Prospectus Supplement dated September 15, 2025, to a Prospectus dated October 13, 2023. Ameren Illinois received net offering proceeds of approximately $358.1 million, before expenses, upon closing of the transaction.

This Current Report on Form 8-K is being filed to report as exhibits certain documents in connection with the offering of the Bonds.

ITEM 9.01 Financial Statements and Exhibits.

(d) Exhibits

Exhibit Number	Title
1.1	Underwriting Agreement relating to the Bonds, dated September 15, 2025, between Ameren Illinois and the several underwriters named therein, for whom KeyBanc Capital Markets Inc., TD Securities (USA) LLC and U.S. Bancorp Investments, Inc. are acting as representatives.
4.1*	General Mortgage Indenture and Deed of Trust, dated as of November 1, 1992, from Ameren Illinois to The Bank of New York Mellon Trust Company, N.A., as successor trustee (1992 Form 10-K, Exhibit 4(cc), File No. 1-3004).
4.2*	Supplemental Indenture, dated as of February 1, 2025, by and between Ameren Illinois and The Bank of New York Mellon Trust Company, N.A., as successor trustee, relating to the Bonds (March 3, 2025 Form 8-K, Exhibit 4.2, File No. 1-3672).
5.1	Opinion of Stephen C. Lee, Esq., Vice President, Interim General Counsel and Secretary of Ameren Illinois, regarding the legality of the Bonds (including consent).
5.2	Opinion of Morgan, Lewis & Bockius LLP regarding the legality of the Bonds (including consent).
104	Cover Page Interactive Data File (formatted as Inline XBRL).

* Incorporated by reference as indicated.

This combined Form 8-K is being filed separately by Ameren Corporation and Ameren Illinois Company (each a “registrant”). Information contained herein relating to any individual registrant has been filed by such registrant on its own behalf. No registrant makes any representation as to information relating to any other registrant.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, each registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. The signature for each undersigned company shall be deemed to relate only to matters having reference to such company or its subsidiaries.

	AMEREN CORPORATION
	(Registrant)
	By:	/s/ Michael L. Moehn
	Name:	Michael L. Moehn
	Title:	Senior Executive Vice President and Chief Financial Officer
	AMEREN ILLINOIS COMPANY
	(Registrant)
	By:	/s/ Leonard P. Singh
	Name:	Leonard P. Singh
	Title:	Chairman and President

Date: September 26, 2025

FAQ

What debt offering did Ameren Illinois Company (AEE) report?

Ameren Illinois Company reported the sale of $350 million principal amount of 5.625% First Mortgage Bonds due 2055 as an additional issuance to a prior 2025 series.

How much cash did Ameren Illinois receive from the new bonds?

Ameren Illinois received net offering proceeds of approximately $358.1 million before expenses from the sale of the 5.625% First Mortgage Bonds due 2055.

Are these Ameren Illinois bonds a new series or an add-on?

These bonds are a further issuance of the 5.625% First Mortgage Bonds due 2055 that were previously issued on March 3, 2025 in the principal amount of $350 million.

Under what registration did Ameren Illinois offer the 5.625% bonds?

The bonds were offered under a Registration Statement on Form S-3 (File No. 333-274977-01), together with a Prospectus dated October 13, 2023 and a Prospectus Supplement dated September 15, 2025.

What documents related to the Ameren Illinois bond sale are filed as exhibits?

Exhibits include the underwriting agreement, the general mortgage indenture and deed of trust, a supplemental indenture, and legal opinions on the validity of the bonds.

Which Ameren entities are covered in this combined Form 8-K?

The combined Form 8-K is filed separately by Ameren Corporation and Ameren Illinois Company, with each registrant responsible only for information relating to itself.