Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax [Line Items]

Income Taxes

INCOME TAXES

Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy		IPL		WPL
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022.

Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months.

Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b)The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior.

In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

IPL [Member]

Income Tax [Line Items]

Income Taxes

INCOME TAXES

Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy		IPL		WPL
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022.

Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months.

Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b)The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior.

In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

WPL [Member]

Income Tax [Line Items]

Income Taxes

INCOME TAXES

Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy		IPL		WPL
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022.

Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months.

Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b)The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior.

In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.