LNT reports Q3 and nine-month 2025 results via 8-K Exhibit 99.1

Rhea-AI Filing Summary

Alliant Energy Corporation filed a Form 8-K to report quarterly results. On November 6, 2025, the company announced financial results for the three and nine months ended September 30, 2025, and furnished the related press release as Exhibit 99.1.

This is a combined filing for Alliant Energy Corporation, Interstate Power & Light Company, and Wisconsin Power & Light Company. The 8-K lists Item 2.02 (Results of Operations and Financial Condition) and includes the press release under Item 9.01(d).

8-K Event Classification

2 items: 2.02, 9.01

2 items

Item 2.02 Results of Operations and Financial Condition Financial

Disclosure of earnings results, typically an earnings press release or preliminary financials.

Item 9.01 Financial Statements and Exhibits Exhibits

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

Understanding 8-K Material Events →

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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) November 6, 2025

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

WISCONSIN POWER & LIGHT COMPANY

(a Wisconsin corporation)

4902 N. Biltmore Lane

Madison, Wisconsin 53718

Telephone (608) 458-3311

Commission File Number - 0-337

IRS Employer Identification Number - 39-0714890

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

This combined Form 8-K is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin 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:

Alliant Energy Corporation, Common Stock, $0.01 Par Value, Trading Symbol 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 ☐

Wisconsin 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 ☐

Wisconsin Power and Light Company ☐

Item 2.02 Results of Operations and Financial Condition.

On November 6, 2025, Alliant Energy Corporation issued a press release announcing its financial results for the three and nine months ended September 30, 2025. A copy of such press release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Item 9.01 Financial Statements and Exhibits.

(a)Not applicable.

(b)Not applicable.

(c)Not applicable.

(d)Exhibits. The following exhibits are being furnished herewith:

Exhibit Number			Description
(99.1)			Alliant Energy Corporation press release dated November 6, 2025
(104)			Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.

ALLIANT ENERGY CORPORATION

Date: November 6, 2025			By: /s/ Dylan M. Syse
			Dylan M. Syse
			Chief Accounting Officer and Controller

INTERSTATE POWER AND LIGHT COMPANY

Date: November 6, 2025			By: /s/ Dylan M. Syse
			Dylan M. Syse
			Chief Accounting Officer and Controller

WISCONSIN POWER AND LIGHT COMPANY

Date: November 6, 2025			By: /s/ Dylan M. Syse
			Dylan M. Syse
			Chief Accounting Officer and Controller

FAQ

What did Alliant Energy (LNT) file?

A Form 8-K reporting quarterly results and furnishing a press release as Exhibit 99.1.

Which period does the announcement cover for LNT?

The financial results cover the three and nine months ended September 30, 2025.

When was the press release issued?

It was issued on November 6, 2025.

Which 8-K items are referenced?

Item 2.02 (Results of Operations and Financial Condition) and Item 9.01(d) (Exhibits).

Which exhibit contains the results details?

Exhibit 99.1 contains the press release with results details.

Is this a combined filing and which entities are included?

Yes. It is combined for Alliant Energy Corporation, Interstate Power & Light Company, and Wisconsin Power & Light Company.