Alliant Energy (NASDAQ: LNT) unit to issue $500M 2031 debt

Who are the joint book-running managers for IPL’s debt offering related to Alliant Energy (LNT)?

Rhea-AI Filing Summary

FAQ

Filing Exhibits & Attachments

Q: What debt offering did Alliant Energy’s subsidiary IPL announce in this Form 8-K for LNT?

Q: What is the interest rate and maturity date of IPL’s new debentures mentioned for LNT?

Q: When is the closing of IPL’s $500 million debenture offering for Alliant Energy (LNT) expected?

Q: How does IPL plan to use the net proceeds of the $500 million debenture offering for LNT?

Q: Under what registration statement is IPL’s $500 million debenture offering for LNT being made?

8-K Event Classification

Key Figures

Key Terms

What debt offering did Alliant Energy’s subsidiary IPL announce in this Form 8-K for LNT?

What is the interest rate and maturity date of IPL’s new debentures mentioned for LNT?

When is the closing of IPL’s $500 million debenture offering for Alliant Energy (LNT) expected?

How does IPL plan to use the net proceeds of the $500 million debenture offering for LNT?

Under what registration statement is IPL’s $500 million debenture offering for LNT being made?

Press Releases

The joint book-running managers are Mizuho Securities USA LLC, PNC Capital Markets LLC, U.S. Bancorp Investments, Inc., and Wells Fargo Securities, LLC. Additional co-managers include Academy Securities, Inc., Fifth Third Securities, Inc., and KeyBanc Capital Markets Inc.

IPL announced the pricing of a public offering of $500 million aggregate principal amount of 5.100% senior debentures due 2031. The debentures are being issued under an existing indenture and registered under an automatic shelf registration statement on Form S-3.

The IPL debentures carry a fixed interest rate of 5.100% and will be due on September 30, 2031. They are part of a $500 million senior debenture issuance in a registered public offering.

The closing of IPL’s $500 million 5.100% senior debenture offering is expected to occur on August 21, 2026, subject to the satisfaction of customary closing conditions as stated in the underwriting agreement and related disclosure.

IPL intends to use the net proceeds to reduce outstanding capital under its receivables purchase and sale program, to reduce outstanding commercial paper, and/or for general corporate purposes, according to the company’s description of the offering.

The offering is registered under an automatic shelf registration statement on Form S-3, Registration No. 333-276062-01, filed with the SEC on December 15, 2023, and supplemented by a prospectus supplement filed on August 18, 2026.

Filing Impact

(Moderate)

Filing Sentiment

(Neutral)

Form Type

8-K

Alliant Energy Corporation (LNT) reported that its Iowa utility subsidiary, Interstate Power and Light Company (IPL), entered into an underwriting agreement to issue $500 million aggregate principal amount of 5.100% Senior Debentures due 2031 in a registered public offering. The debentures will be issued under IPL’s existing 2003 indenture with The Bank of New York Mellon Trust Company, N.A. as trustee, pursuant to an automatic shelf registration statement on Form S-3.

The debentures have a stated maturity of September 30, 2031, and the offering is expected to close on August 21, 2026, subject to customary closing conditions. IPL states that net proceeds are intended to be used to reduce outstanding capital under its receivables purchase and sale program, to reduce outstanding commercial paper, and/or for general corporate purposes. The deal is being underwritten by a syndicate led by Mizuho Securities USA LLC, PNC Capital Markets LLC, U.S. Bancorp Investments, Inc., and Wells Fargo Securities, LLC as joint book-running managers.

2 items: 8.01, 9.01

2 items

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

Aggregate principal amount: $500 million Coupon rate: 5.100% Maturity date: September 30, 2031 +2 more

5 metrics

Aggregate principal amount $500 million Senior debentures issued by IPL in the public offering

Coupon rate 5.100% Interest rate on IPL’s senior debentures due 2031

Maturity date September 30, 2031 Stated due date of IPL’s senior debentures

Expected closing date August 21, 2026 Anticipated closing of the debenture offering, subject to conditions

Registration statement number 333-276062-01 Automatic shelf registration statement on Form S-3 for the offering

senior debentures, automatic shelf registration statement, prospectus supplement, receivables purchase and sale program, +1 more

5 terms

senior debentures financial

"aggregate principal amount of 5.100% senior debentures due 2031"

Senior debentures are long-term loans a company issues to investors that promise regular interest payments and return of principal but usually do not have specific assets pledged as collateral. They take priority over other unsecured or subordinated debt if the company goes into bankruptcy, so they are typically safer than lower-ranked bonds; that priority affects the interest rate investors demand—think of them as a line in the repayment queue placed ahead of many other creditors.

automatic shelf registration statement regulatory

"pursuant to an automatic shelf registration statement on Form S-3"

An automatic shelf registration statement is a pre-approved filing that companies submit to securities regulators, allowing them to sell new shares or bonds quickly and efficiently when needed. It acts like a standing permit, enabling the company to raise money without going through a lengthy approval process each time, which can be helpful for responding promptly to market opportunities or needs. For investors, it provides transparency about the company's ability to raise funds and signals planning flexibility.

prospectus supplement regulatory

"supplemented by a Prospectus Supplement setting forth the terms"

A prospectus supplement is an additional document provided alongside a company's main offering details, offering updated or extra information about a specific financial product being sold. It helps investors understand the latest terms, risks, and details of the investment, similar to how an update or revision clarifies or expands on original instructions, ensuring they have current and complete information before making a decision.

receivables purchase and sale program financial

"reduce outstanding capital under its receivables purchase and sale program"

indenture financial

"to be issued under an Indenture dated as of August 20, 2003"

An indenture is a legal agreement between a company that borrows money by issuing bonds and the people who buy those bonds. It explains the rules the company must follow, like paying back the money and keeping certain financial promises. This document helps both sides understand their rights and responsibilities.

IPL announced the pricing of a public offering of $500 million aggregate principal amount of 5.100% senior debentures due 2031. The debentures are being issued under an existing indenture and registered under an automatic shelf registration statement on Form S-3.

The IPL debentures carry a fixed interest rate of 5.100% and will be due on September 30, 2031. They are part of a $500 million senior debenture issuance in a registered public offering.

The closing of IPL’s $500 million 5.100% senior debenture offering is expected to occur on August 21, 2026, subject to the satisfaction of customary closing conditions as stated in the underwriting agreement and related disclosure.

IPL intends to use the net proceeds to reduce outstanding capital under its receivables purchase and sale program, to reduce outstanding commercial paper, and/or for general corporate purposes, according to the company’s description of the offering.

The offering is registered under an automatic shelf registration statement on Form S-3, Registration No. 333-276062-01, filed with the SEC on December 15, 2023, and supplemented by a prospectus supplement filed on August 18, 2026.

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Understanding 8-K Material Events →

Available on EDGAR 08/24/2026 - 05:59 PM Accepted by SEC EDGAR 08/21/2026 - 08:45 AM

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): August 21, 2026

Name of Registrant, State of Incorporation, Address of Principal Executive Offices, Telephone Number, Commission File Number, IRS Employer Identification Number

ALLIANT ENERGY CORPORATION

(a Wisconsin corporation)

4902 N. Biltmore Lane

Madison, Wisconsin 53718

Telephone (608)

458-3311

Commission File Number -

1-9894

IRS Employer Identification Number -

39-1380265

INTERSTATE POWER & LIGHT COMPANY

(an Iowa corporation)

Alliant Energy Tower

Cedar Rapids, Iowa 52401

Telephone (319)

786-4411

Commission File Number -

1-4117

IRS Employer Identification Number -

42-0331370

(Former name or former address, if changed since last report.)

This combined Form

8-K

is separately filed by Alliant Energy Corporation and Interstate Power and Light Company.

Check the appropriate box below if the Form

8-K

filing is intended to simultaneously satisfy the filing obligation of the registrant 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	Name of Each Exchange on Which Registered
Alliant Energy Corporation Common Stock, $0.01 Par Value	LNT	Nasdaq Global Select Market

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).

Alliant Energy Corporation - Emerging growth company ☐

Interstate Power and Light Company - Emerging growth 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.

Alliant Energy Corporation ☐

Interstate Power and Light Company ☐

Item 8.01

Other Events.

On August 18, 2026, Interstate Power and Light Company (“IPL”), a subsidiary of Alliant Energy Corporation, entered into an Underwriting Agreement (the “Underwriting Agreement”) with Mizuho Securities USA LLC, PNC Capital Markets LLC, U.S. Bancorp Investments, Inc., and Wells Fargo Securities, LLC, as representatives of the several underwriters listed therein (the “Underwriters”), pursuant to which IPL agreed to sell, and the Underwriters agreed to purchase, subject to the terms and conditions set forth therein, $500 million aggregate principal amount of IPL’s 5.100% Senior Debentures due 2031 (the “Debentures”), in a public offering (the “Offering”). The Debentures are to be issued under an Indenture dated as of August 20, 2003, between IPL and The Bank of New York Mellon Trust Company, N.A., as successor trustee (the “Indenture”), pursuant to an Officer’s Certificate provided pursuant to the Indenture setting forth the terms of the Debentures, dated as of August 21, 2026 (the “Certificate”). The Offering is expected to close, subject to standard closing conditions, on August 21, 2026.

The Debentures are registered under the Securities Act of 1933, as amended, pursuant to an automatic shelf registration statement on Form S-3 (Registration No. 333-276062-01) that IPL filed with the Securities and Exchange Commission (the “SEC”) on December 15, 2023 (the “Registration Statement”). The Registration Statement was supplemented by a Prospectus Supplement setting forth the terms of the Debentures that IPL filed with the SEC on August 18, 2026.

This Current Report on Form 8-K is being filed for the purpose of filing exhibits to the Registration Statement relating to the public offering of the Debentures, and all such exhibits are hereby incorporated into the Registration Statement by reference. The Underwriting Agreement is filed as Exhibit 1.1 and the Certificate is filed as Exhibit 4.1 to this Form 8-K.

On August 18, 2026, IPL issued a press release announcing that it had priced the Offering. The press release is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Ashurst Perkins Coie US LLP, counsel to IPL, has issued an opinion to IPL, dated August 21, 2026, regarding the legality of the Debentures upon issuance thereof, and Simmons Perrine PLC, Iowa counsel to IPL, has issued an opinion to IPL, dated August 21, 2026, regarding certain legal matters relating to Iowa law. The opinions are filed as Exhibit 5.1 and Exhibit 5.2, respectively, hereto.

Item 9.01

Financial Statements and Exhibits.

(d)

Exhibits


Exhibit No.		Description

1.1		Underwriting Agreement, dated August 18, 2026, among Interstate Power and Light Company and the underwriters named therein.

4.1		Officer’s Certificate, dated August 21, 2026, creating the 5.100% Senior Debentures due 2031 of Interstate Power and Light Company.

5.1		Opinion of Ashurst Perkins Coie US LLP, dated August 21, 2026, with respect to the 5.100% Senior Debentures due 2031 of Interstate Power and Light Company.

5.2		Opinion of Simmons Perrine PLC, dated August 21, 2026, with respect to the 5.100% Senior Debentures due 2031 of Interstate Power and Light Company.

23.1		Consent of Ashurst Perkins Coie US LLP (contained in Exhibit 5.1 hereto).

23.2		Consent of Simmons Perrine PLC (contained in Exhibit 5.2 hereto).

99.1		Press Release of Interstate Power and Light Company, dated August 18, 2026.

104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, Alliant Energy Corporation and Interstate Power and Light Company have each duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Exhibit 99.1

LOGO


				Interstate Power and Light Company
				An Alliant Energy Company

				Corporate Headquarters 4902 North Biltmore Lane Madison, WI 53718-2148


*News Release*
FOR IMMEDIATE RELEASE				Media Hotline: (608) 458-4040
				Investor Relations: Susan Gille: (608) 458-3956

Interstate Power and Light Company Prices Debt Offering

$500 million in senior debentures will be due in 2031

Madison, Wisconsin – August 18, 2026 – Interstate Power and Light Company (“IPL”), a wholly owned subsidiary of Alliant Energy Corporation (NASDAQ: LNT), announced the pricing of its public offering of $500 million aggregate principal amount of 5.100% senior debentures due 2031. The senior debentures will be due on September 30, 2031. IPL intends to use the net proceeds from this offering to reduce outstanding capital under its receivables purchase and sale program, to reduce outstanding commercial paper, and/or for general corporate purposes. The closing of the offering is expected to occur on August 21, 2026, subject to the satisfaction of customary closing conditions.

The offering was marketed through a group of underwriters consisting of Mizuho Securities USA LLC, PNC Capital Markets LLC, U.S. Bancorp Investments, Inc., and Wells Fargo Securities, LLC as joint book-running managers, and Academy Securities, Inc., Fifth Third Securities, Inc., KeyBanc Capital Markets Inc. and TD Securities (USA) LLC as co-managers.

The offering is being made only by means of a prospectus supplement and accompanying prospectus which are part of a shelf registration statement IPL filed with the Securities and Exchange Commission (the “Commission”). Copies may be obtained by calling Mizuho Securities USA LLC toll free at 1-866-271-7403, PNC Capital Markets LLC toll free at 1-855-881-0697, U.S. Bancorp Investments, Inc. toll free at 1-877-558-2607 and Wells Fargo Securities, LLC toll free at 1-800-645-3751. Electronic copies of these documents will be available from the Commission’s website at www.sec.gov.

This press release does not constitute an offer to sell or the solicitation of an offer to buy these securities, nor will there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Alliant Energy

Alliant Energy Corporation’s Iowa utility subsidiary, Interstate Power and Light Company (IPL), utilizes the trade name of Alliant Energy (NASDAQ:LNT). The Iowa utility is based in Cedar Rapids, Iowa.

Forward-Looking Statements

This press release includes forward-looking statements. These statements involve inherent risks and uncertainties that could cause actual results to differ materially from those projected or anticipated, including risks related to the proposed offering, the anticipated use of proceeds from the sale of the senior debentures and other risks outlined in IPL’s public filings with the Commission, including IPL’s most recent annual report on Form 10-K and subsequent Quarterly Reports on Form 10-Q. All information provided in this news release speaks as of the date hereof. Except as otherwise required by law, IPL undertakes no obligation to update or revise its forward-looking statements.

Source: View Original Filing on SEC EDGAR

6 documents

ALLIANT ENERGY CORPORATION

Date: August 21, 2026

/s/ Robert J. Durian

Robert J. Durian

Executive Vice President and Chief Financial Officer

EX-99.1 EX-99.1 8.1 KB