Vanguard Portfolio Management reports 5.68% stake in Alliant Energy (LNT)

Rhea-AI Filing Summary

Vanguard Portfolio Management reports beneficial ownership of 14,626,154 shares of Alliant Energy Corp. The position represents 5.68% of the outstanding common stock as reported for the period ending 03/31/2026. The filer discloses sole voting power over 31,148 shares and sole dispositive power over 14,626,154 shares. The filing states these holdings include securities held for Vanguard funds and managed accounts and is signed on 04/28/2026.

Insights

Institutional Ownership Analyst

Vanguard holds a reported 5.68% stake in Alliant Energy, showing material institutional ownership.

Vanguard Portfolio Management discloses beneficial ownership of 14,626,154 shares, representing 5.68% of common stock as of 03/31/2026. The filing clarifies that holdings include shares held for Vanguard funds and managed accounts under the reporting unit.

Key dependencies include continued aggregation rules for affiliated Vanguard entities and any future schedule amendments; subsequent filings would update position size or voting authority.

Key Figures

Shares beneficially owned: 14,626,154 shares Percent of class: 5.68% Sole voting power: 31,148 shares +3 more

6 metrics

Shares beneficially owned 14,626,154 shares beneficial ownership as of 03/31/2026

Percent of class 5.68% percent of common stock reported

Sole voting power 31,148 shares sole power to vote or direct the vote

Sole dispositive power 14,626,154 shares sole power to dispose or direct disposition

Reporting period 03/31/2026 period ending date for reported holdings

Signature date 04/28/2026 date the Schedule 13G was signed

Key Terms

beneficially owned, sole dispositive power, Schedule 13G

3 terms

beneficially owned regulatory

"reflects the securities beneficially owned, or deemed to be beneficially owned"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 14626154"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Schedule 13G regulatory

"Item 1. | (a) | Name of issuer: Alliant Energy Corp"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Alliant Energy Corp

(Name of Issuer)

Common Stock

(Title of Class of Securities)

018802108

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 018802108

1

Names of Reporting Persons

Vanguard Portfolio Management

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 31,148.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 14,626,154.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

14,626,154.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.68 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Vanguard Portfolio Management LLC and the following affiliates of Vanguard Portfolio Management LLC or business divisions of such affiliates: Vanguard Fiduciary Trust Company and Vanguard Global Advisers, LLC. This Schedule 13G includes securities held by Vanguard funds, or sleeves thereof, over which Vanguard Portfolio Management LLC exercises dispositive power, in addition to securities held by clients over which the affiliates or business divisions of such affiliates indicated above exercise dispositive and/or voting power. This Schedule 13G does not include securities, if any, beneficially owned by other subsidiaries or affiliates of Vanguard Portfolio Management LLC, or business divisions of such subsidiaries whose ownership of securities is disaggregated from that of the reporting business unit in accordance with such release.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Alliant Energy Corp
(b)	Address of issuer's principal executive offices: 4902 North Biltmore Lane, Madison, WI, 53718
Item 2.
(a)	Name of person filing: Vanguard Portfolio Management
(b)	Address or principal business office or, if none, residence: 100 Vanguard Blvd,, Malvern, PA, 19355
(c)	Citizenship: PA
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 018802108
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 14626154
(b)	Percent of class: 5.68 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 31148
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 14626154
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Vanguard Portfolio Management, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.No one other person's interest in the securities reported herein is more than 5%.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Vanguard Portfolio Management

Signature:	Ashley Grim
Name/Title:	Head of Global Fund Administration
Date:	04/28/2026

FAQ

What stake does Vanguard Portfolio Management report in Alliant Energy (LNT)?

Vanguard reports beneficial ownership of 14,626,154 shares, representing 5.68% of Alliant Energy common stock as of 03/31/2026. The filing attributes dispositive power to Vanguard Portfolio Management for these shares.

How much voting power does Vanguard hold in this 13G filing?

The filing discloses sole voting power over 31,148 shares of Alliant Energy. It lists 0 shares as shared voting power and attributes dispositive control to Vanguard Portfolio Management.

Does the Schedule 13G indicate shares are held for funds or clients?

Yes. The filing states the reported shares include securities held by Vanguard funds and managed accounts for which Vanguard Portfolio Management or its affiliates exercise dispositive authority.

What is the reporting period and signature date on the filing?

The ownership is reported for the period ending 03/31/2026, and the Schedule 13G is signed by Ashley Grim on 04/28/2026 as Head of Global Fund Administration.