Document


			Page Number
REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM			3
FINANCIAL STATEMENTS
Statements of Net Assets Available for Benefits as of December 31, 2023 and 2022			4
Statement of Changes in Net Assets Available for Benefits for the Year Ended December 31, 2023			5
NOTES TO FINANCIAL STATEMENTS
1. Description of the Plan			6
2. Summary of Significant Accounting Policies			7
3. Tax Status			8
4. Plan Termination Provisions			8
5. Withdrawals and Distributions			8
6. Fair Value Measurements			8
7. Related Party Transactions			9
8. Reconciliation to Form 5500			10
SUPPLEMENTAL SCHEDULE
Form 5500, Schedule H, Part IV, line 4i - Schedule of Assets (Held at End of Year) as of December 31, 2023			11
Note: All other schedules required by Section 2520.103-10 of the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974 have been omitted because they are not applicable.
SIGNATURES			12
EXHIBIT INDEX			13
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM			14

We have audited the accompanying statements of net assets available for benefits of the Alliant Energy Corporation 401(k) Savings Plan (the "Plan") as of December 31, 2023 and 2022, the related statement of changes in net assets available for benefits for the year ended December 31, 2023, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2023 and 2022, and the changes in net assets available for benefits for the year ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

These financial statements are the responsibility of the Plan's management. Our responsibility is to express an opinion on the Plan's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Plan in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

The supplemental schedule of assets (held at end of year) as of December 31, 2023, has been subjected to audit procedures performed in conjunction with the audit of the Plan's financial statements. The supplemental schedule is the responsibility of the Plan's management. Our audit procedures included determining whether the supplemental schedule reconciles to the financial statements or the underlying accounting and other records, as applicable, and performing procedures to test the completeness and accuracy of the information presented in the supplemental schedule. In forming our opinion on the supplemental schedule, we evaluated whether the supplemental schedule, including its form and content, is presented in compliance with the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. In our opinion, such schedule is fairly stated, in all material respects, in relation to the financial statements as a whole.


	December 31, 2023	December 31, 2022
Investments at fair value (Refer to Note 6)	$1,231,566,112	$1,070,199,666
Fully benefit-responsive investment contracts at contract value (Refer to Note 2)	85,672,495	95,043,546
Notes receivable from participants	10,085,872	9,004,229
Employer contribution receivable	742,721	758,485
Net assets available for benefits	$1,328,067,200	$1,175,005,926


						For the Year Ended December 31,
						2023
Net assets available for benefits - beginning of year						$1,175,005,926
Contributions:
Cash contributions from employees						42,545,907
Cash contributions from employer						29,014,709
Rollovers from other qualified plans						2,778,734
Total contributions						74,339,350
Investment income:
Interest and dividends						19,238,636
Net appreciation in fair value of investments						177,920,124
Net investment income						197,158,760

Interest income on notes receivable from participants						546,235
Distributions to participants						(118,983,071)
Net increase						153,061,274
Net assets available for benefits - end of year						$1,328,067,200

The Alliant Energy Corporation 401(k) Savings Plan (the Plan) is a qualified defined contribution plan under Section 401(k) of the Internal Revenue Code (the Code), as amended, and meets the applicable requirements of the Employee Retirement Income Security Act of 1974, as amended. The following brief description of the Plan is provided for general information purposes only. More complete information regarding the Plan is provided in the plan document and summary plan description, which have been made available to all eligible Plan participants (participants). The Plan is administered by the Alliant Energy Corporation Benefit Plans Committee (the Committee) and the Plan sponsor is Alliant Energy Corporate Services, Inc. (a direct subsidiary of Alliant Energy Corporation). The Committee reserves the right to terminate, amend or modify the Plan if future conditions warrant such action.

Any regular employee of Alliant Energy Corporation and its participating subsidiaries (the Company) age 18 and over may participate in the Plan. Regular full-time employees and regular part-time employees customarily scheduled to work at least half-time may participate immediately following 30 consecutive days of service. Part-time employees customarily scheduled to work less than half-time may participate after 12 months of service during which they have earned at least 1,000 paid hours. An initial automatic 8% pre-tax employee contribution rate has been applied to newly hired employees, unless the employee made a contrary election within 30 days of their hire date. Participant contributions are invested in an age appropriate target date fund until changed at the participant’s discretion. The Plan also applies an automatic deferral increase for non-bargaining and certain bargaining unit employees contributing less than a 10% employee contribution rate. The employees’ contribution rate will automatically increase by 1% each year until they reach a 10% employee contribution rate. Employees have the option of opting out of the automatic deferral increase.

An Employee Stock Ownership Plan is in place within the Plan. Under these provisions, participants have the option to elect to receive a cash distribution from the Plan for any dividends paid on Company common stock within the Plan or to have the dividends reinvested in additional shares based on the current market price.

The Company provides matching contributions of $0.50 for each $1 contributed by the participant up to the first 8% of each respective participant’s eligible compensation. In addition, the Company provides a contribution into each active employee’s 401(k) account each pay period based on a percentage of their eligible compensation (non-elective Company cash contribution) as follows:

Company matching contributions and the non-elective Company cash contributions are invested at each participant’s discretion. Participants may subsequently re-designate the distribution of future contributions or transfer existing balances between investment funds on a daily basis, subject to the limits set forth in the Plan. The Plan allows participants to transfer vested balances to an in-plan Roth conversion account within the Plan, subject to the limits and terms set forth in the Plan.

There are certain exceptions to the 8% Company matching contributions and non-elective Company cash contributions described above for bargaining unit employees. These exceptions are dependent on the bargaining unit in which the employee participates and the employee’s date of hire. These exceptions include certain employees being ineligible for the non-elective Company cash contribution and the Company matching contribution being limited to $0.50 for each $1 contributed by the participant up to the first 6% of each respective participant’s eligible compensation. There are also exceptions for certain bargaining unit employees who are eligible for a Company matching contribution of $0.50 for each $1 contributed by the participant up to the first 10% of each respective participant’s eligible compensation. Effective during the year ended December 31, 2022, certain bargaining unit employees also receive an additional annual Company contribution of $500 to $1,000 through January 2025.

An “additional” Company contribution is contributed to the accounts of active participants, as of the last day of the Plan year, who contributed at least the maximum level of their compensation eligible to be matched by the Company and did not receive the maximum level of Company matching contributions based on their contributions during the Plan year.

Participants are immediately vested in their respective employee and Company contributions, except for the non-elective Company cash contribution which is subject to a three-year cliff vesting schedule for all new hires. At December 31, 2023 and 2022, forfeited nonvested accounts totaled $478,808 and $254,509, respectively. These accounts will be used to reduce future Company contributions. In 2023, Company contributions were reduced by $136,635 from forfeited nonvested accounts.

Contributions under the Plan are held and invested, until distribution, in a trust fund maintained by Empower Trust Company, LLC (the Trustee, f/k/a Great-West Trust Company, LLC). Individual accounts are maintained by Empower Plan Services, LLC (the Recordkeeper, f/k/a Great-West Financial Retirement Plan Services, LLC) for each participant. The Self-Managed Brokerage Accounts service provider is Charles Schwab & Co. Each participant’s account is credited with the participant’s contributions, Company contributions and an allocation of Plan earnings, and charged with withdrawals and an allocation of Plan losses and administrative expenses, as applicable. Allocations are based on participant earnings or account balances, as defined. Participant rollovers are allowed into the Plan from other qualified plans. The benefit to which a participant is entitled is the benefit that can be provided from the participant’s vested account balance.

The Plan has provisions under which participants who are active employees may take loans up to the lesser of $50,000 or 50% of their total account balance (a $1,000 minimum loan amount and a maximum of three loans for each participant also apply). The Committee determines the loan interest rate pursuant to the Plan. Interest rates on participant loans outstanding ranged from 4.25% to 9.50% and 4.25% to 9.25% at December 31, 2023 and 2022, respectively. Principal and interest are repaid bi-weekly through employee payroll deductions.

NOTE 2(b) Accounting for Fully Benefit-Responsive Contracts - In accordance with Financial Accounting Standards Board (FASB) authoritative guidance, which defines reporting of fully benefit-responsive contracts held by defined-contribution pension plans, the statements of net assets available for benefits present investments at fair value except for fully benefit-responsive contracts, which are reported at contract value. Contract value is the relevant measure for the fully benefit-responsive investment contracts because contract value is the amount participants normally would receive if they were to initiate permitted transactions under the terms of the Plan. Certain events, such as a Plan termination or merger, initiated by the Plan sponsor, may limit the ability of the Plan to transact at contract value or may allow for the termination of the wrapper contract at less than contract value. The Committee believes the likelihood of events occurring that may limit the ability of the Plan to transact at contract value is not probable.

All guaranteed investment contracts held by the Plan are fully benefit-responsive contracts and at December 31, 2023 and 2022 all were synthetic. The contract value of all synthetic guaranteed investment contract investments was $85,672,495 and $95,043,546 at December 31, 2023 and 2022, respectively. The synthetic guaranteed investment contracts are comprised of investments in common collective trusts owned by the Plan and an investment contract issued by an insurance company or other financial institution, designed to provide a contract value “wrapper” around the fixed income portfolio to guarantee a specific interest rate. The guaranteed investment contract wrappers provide protection when the market value of the underlying assets is less than the contract value.

NOTE 2(c) Valuation of Investments and Income Recognition - The Plan’s investments are stated at fair value except for fully benefit-responsive investment contracts, which are reported at contract value. Plan investments are carried at fair value as determined by quoted market prices or the net asset value (NAV), as a practical expedient, of shares held by the Plan on the valuation date. Interest income is accrued when earned. Dividend income is recorded on the ex-dividend date. Investment transactions are recorded on the trade date.

NOTE 2(d) Net Appreciation/Depreciation in Fair Value of Investments - Net realized and unrealized appreciation (depreciation) includes the Plan’s gains and losses on investments bought and sold as well as held during the year and is recorded in the accompanying statement of changes in net assets available for benefits as “Net appreciation or (depreciation) in fair value of investments.”

NOTE 2(g) Expenses - All expenses paid through the Plan are recorded with investment earnings (losses) in the accompanying statement of changes in net assets available for benefits. Recordkeeping fees and expenses incurred in maintaining Self-Managed Brokerage Accounts are reported separately from investment earnings on individual participant statements and are paid by the Plan participants. Investment management fees are paid from investment earnings prior to crediting earnings to the individual participant account balances, but can be identified in the investment fund information supplied to participants from the Recordkeeper. Certain other Plan administrative expenses are absorbed by the Company.

NOTE 2(h) Use of Estimates - The preparation of financial statements in conformity with GAAP requires the Plan administrator to make estimates and assumptions that affect the reported amounts of net assets available for benefits at the date of the financial statements and the reported amounts of changes in net assets available for benefits during the reporting period. Actual results could differ from those estimates.

NOTE 2(i) Risk and Uncertainties - The Plan invests in various investments, including registered investment companies, common/collective trusts, common stock of the Company and synthetic investment contracts. The Plan also offers a Self-Managed Brokerage Account option, which allows participants to invest in a wide range of mutual funds and exchange traded funds. Investments, in general, are exposed to various risks, such as interest rate, credit and overall market volatility risks. Market risks include global events which could impact the value of investment securities, such as a pandemic or international conflict. Due to the level of risk associated with certain investments, it is reasonably possible that changes in the values of certain investments may occur in the near term and that such changes could materially affect the amounts reported in the financial statements. As of December 31, 2023 and 2022, there were significant concentrations of investments in the State Street S&P 500 Index Securities Lending Series Fund, American Funds EuroPacific Growth Fund, Northern Trust Collective Extended Equity Market Index Fund and Winslow Large Cap Growth Fund.

The Internal Revenue Service (IRS) has determined and informed the Company by a letter dated May 22, 2017, that the Plan and related trust are designed in accordance with the applicable sections of the Code. The Plan has been amended since receiving the determination letter. The Committee and the Plan’s tax counsel believe that the Plan is designed and is currently being operated in compliance with the applicable requirements of the Code. Therefore, no provision for income taxes has been included in the Plan’s financial statements.

Withdrawals from participants’ account balances are allowed when participants reach age 59-1/2. Withdrawals are also allowed due to special “hardship” circumstances. Terminated employees may take distributions at any age, subject to penalties based upon age at the time of distribution. Automatic distributions from the Plan will be made upon termination of employment (by retirement, death, disability or otherwise) if the participant’s account balance is less than $5,000. Beneficiaries of deceased employees can remain in the Plan. If a withdrawing participant’s account balance is less than $5,000, and the participant does not make an election to either have the account paid as a direct rollover or as a cash payment, the distribution will be paid as a direct rollover to an individual retirement account established for the participant. If a withdrawing participant’s account balance exceeds $5,000, the participant may elect to defer payment until he or she is age 72. Distributions can be either in the form of a lump sum, partial distribution or substantially equal monthly, quarterly, semiannual or annual installments. The unpaid portion of all loans made to the participant, including accrued interest, will be deducted from the amount of the participant account to be distributed. Distributions payable to participants at December 31, 2023 and 2022 were $0.

Valuation Hierarchy and Techniques - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and a description of the Plan’s assets and valuation techniques for each are as follows:

Level 1 - Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Level 1 Plan assets include investments in registered investment companies and common stocks and are valued at the closing price reported in the active market in which the individual securities are traded. Assets of Self-Managed brokerage accounts at December 31, 2023 and 2022 were limited to investments in registered investment companies.

The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability.

The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.


	Fair Value Measurements	Level 1
Assets at December 31, 2023:
Registered investment companies:
International - developed markets	$168,682,853	$168,682,853
U.S. large cap value	126,876,312	126,876,312
Fixed income funds	75,154,794	75,154,794





Common stock	104,031,206	104,031,206
Self-Managed brokerage accounts	13,679,408	13,679,408
Total assets in the fair value hierarchy	488,424,573	$488,424,573
Assets measured at NAV (a)	743,141,539
Total assets at fair value	$1,231,566,112


	Fair Value Measurements	Level 1
Assets at December 31, 2022:
Registered investment companies:
International - developed markets	$149,137,563	$149,137,563
U.S. large cap value	110,174,505	110,174,505
Fixed income funds	69,063,466	69,063,466





Common stock	116,328,445	116,328,445
Self-Managed brokerage accounts	11,254,727	11,254,727
Total assets in the fair value hierarchy	455,958,706	$455,958,706
Assets measured at NAV (a)	614,240,960
Total assets at fair value	$1,070,199,666

(a)In accordance with FASB authoritative guidance, certain investments that are measured at fair value using the NAV practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of net assets available for benefits. These Plan assets include investments in common/collective trusts, which are valued at the NAV of shares held by the Plan which is based on the fair market value of the underlying investments in the common/collective trusts. The common/collective trusts underlying assets primarily consist of traded securities that have a variety of investment strategies including domestic and international equity and fixed income funds. There are no no unfunded commitments and no participant redemption restrictions for these investments and no redemption notice period applicable to the Plan.

Certain Plan investments are shares of common stock of the Company. As of December 31, 2023 and 2022, the Plan held 2,027,899 and 2,107,018 shares of Alliant Energy Corporation common stock with a cost basis of $65,589,856 and $65,518,188, and fair value of $104,031,206 and $116,328,445, respectively. In 2023 and 2022, the Plan recorded dividend income of $3,705,071 and $3,690,250, respectively, from investments in common stock of the Company. These transactions qualify as exempt party-in-interest transactions.

Certain of the investment options offered under the Self-Managed Brokerage Accounts are funds managed by Charles Schwab & Co., the service provider of the Self-Managed Brokerage Accounts and therefore, these transactions qualify as exempt party-in-interest transactions. Notes receivable from participants transactions also qualify as exempt party-in-interest transactions.

Net assets available for benefits in the accompanying financial statements report fully benefit-responsive investment contracts at contract value; however, the contracts are recorded at fair value in the Plan’s Form 5500. Certain loans in default have been recorded as distributions in the Plan’s Form 5500; however, these loans have been maintained as notes receivable from participants in the net assets available for benefits in the accompanying financial statements. If applicable, distributions payable to participants are not included as a liability within net assets available for benefits in the accompanying financial statements, however, they are recorded as liabilities in the Plan’s Form 5500. There were no distributions payable as of December 31, 2023 and 2022. The following table reconciles net assets available for benefits per the financial statements to the Plan’s Form 5500 as filed by the Plan:


	2023	2022
Net assets available for benefits per financial statements	$1,328,067,200	$1,175,005,926
Adjustments:
Contract value to fair value for fully benefit-responsive investment contracts	(5,406,953)	(7,569,445)
Deemed distributions of participant loans	(1,482,876)	(1,395,323)
Amounts reported per Form 5500	$1,321,177,371	$1,166,041,158

Identity of issue, borrower,

Description of investment including maturity date,

lessor, or similar party

rate of interest, collateral, par or maturity value

Cost (a)

Current Value

Registered Investment Companies

American Funds EuroPacific Growth Fund, 3,083,782 class R6 shares

$168,682,853

Dodge & Cox Stock Fund, 520,924 class X shares

126,876,312

PIMCO Total Return Fund, 8,272,197 class I shares

71,554,508

Vanguard Short-Term Inflation-Protected Securities Index Fund, 151,209 Admiral shares

3,600,286

Common/Collective Trusts

State Street S&P 500 Index Securities Lending Series Fund, 13,534,052 class II shares

280,236,075

Abrdn Emerging Markets Equity Collective Fund, 1,967,312 class A shares

23,647,094

Winslow Large Cap Growth Fund, 1,491,912 class I shares

166,885,249

Northern Trust Collective Extended Equity Market Index Fund - Lending, 139,235 shares

155,097,919

State Street U.S. Bond Index Securities Lending Series Fund, 10,752,925 class XIV shares

114,163,801

JPMCB Intermediate Bond Fund (b), 3,408,291 shares

60,190,422

JPMCB Intermediate Income Bond Fund (b), 1,792,421 shares

20,075,120

JPMCB Liquidity Fund (b) 3,111,401 shares

3,111,401

Corporate Stocks: Common

Alliant Energy Corporation common stock (b), 2,027,899 shares

104,031,206

Participant-Directed Brokerage Accounts

Self-Managed Brokerage Accounts (b)

13,679,408

Participant Promissory Notes (b)

Maximum allowable loans per participant - $50,000

Various interest rates - 4.25% to 9.5%

Primarily maturing within 5 years

10,085,872

$1,321,917,526


Age Plus Years of Service						Company Contribution
Less than or equal to 49						4%
50 - 69						5%
70+						6%


Eligible employee annual contribution limit as a percentage of compensation			50%
Maximum annual contribution limit (a)			$22,500


			Net Increase
Amounts reported per financial statements			$153,061,274
Adjustments:
Changes in adjustment from contract value to fair value for fully benefit-responsive investment contracts			2,162,492
Changes in deemed distributions of participant loans			(87,553)
Amounts reported per Form 5500			$155,136,213


			ALLIANT ENERGY CORPORATION
			401(k) SAVINGS PLAN

			/s/ L. Diane Cooke
			L. Diane Cooke

			The foregoing person is the Vice President
			Human Resources of Alliant Energy Corporation and
			Alliant Energy Corporate Services, Inc., and the
			chair of the Alliant Energy Corporation
			Benefit Plans Committee.


x			ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934


¨			TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934