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Income Taxes | 12 Months Ended
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Dec. 31, 2013
Income Tax [Line Items] |
Income Taxes | INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $4.4 |  |  |  | ($29.3 | ) |  |  | $58.6 |  |  |  | $11.7 |  |  |  | ($7.7 | ) |  |  | $54.5 |  |  |  | ($5.7 | ) |  |  | $7.2 |  |  |  | ($4.3 | )
State | (3.6 | ) |  | 11.6 |  |  | 15.7 |  |  | (0.1 | ) |  | 9.1 |  |  | 20.0 |  |  | 6.0 |  |  | (0.9 | ) |  | (7.1 | )
IPL’s tax benefit riders | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 123.9 |  |  | 157.8 |  |  | 99.0 |  |  | 20.0 |  |  | 37.4 |  |  | (11.6 | ) |  | 92.7 |  |  | 81.1 |  |  | 111.3 |
State | 15.6 |  |  | 23.9 |  |  | (16.8 | ) |  | (0.8 | ) |  | 3.2 |  |  | (16.4 | ) |  | 11.8 |  |  | 20.3 |  |  | 19.0 |
Production tax credits | (31.0 | ) |  | (24.8 | ) |  | (27.1 | ) |  | (14.4 | ) |  | (12.5 | ) |  | (12.3 | ) |  | (16.6 | ) |  | (12.3 | ) |  | (14.8 | )
Investment tax credits | (1.6 | ) |  | (1.7 | ) |  | (1.8 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (1.0 | ) |  | (1.1 | ) |  | (1.2 | )
Provision recorded as a change in uncertain tax positions: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current | — |  |  | 8.0 |  |  | 16.3 |  |  | — |  |  | 8.1 |  |  | 16.6 |  |  | — |  |  | (0.1 | ) |  | (0.3 | )
Deferred | (0.4 | ) |  | (7.6 | ) |  | (38.3 | ) |  | — |  |  | (8.2 | ) |  | (17.6 | ) |  | (0.4 | ) |  | 0.6 |  |  | (20.7 | )
Provision recorded as a change in accrued interest | (0.5 | ) |  | (0.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.3 | ) |  | (0.3 | ) |  | 0.4 |  |  | (0.2 | ) |  | — |
|  | $53.9 |  |  |  | $89.4 |  |  |  | $69.2 |  |  |  | ($37.9 | ) |  |  | ($19.8 | ) |  |  | ($3.6 | ) |  |  | $87.2 |  |  |  | $94.6 |  |  |  | $81.9 |
Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.7 |  |  | 5.7 |  |  | 4.6 |  |  | 5.4 |  |  | 5.8 |  |  | 4.3 |  |  | 6.0 |  |  | 5.5 |  |  | 5.0 |
IPL’s tax benefit riders | (12.1 | ) |  | (11.2 | ) |  | (8.8 | ) |  | (34.8 | ) |  | (37.0 | ) |  | (26.5 | ) |  | — |  |  | — |  |  | — |
Production tax credits | (7.1 | ) |  | (5.8 | ) |  | (6.6 | ) |  | (9.5 | ) |  | (9.6 | ) |  | (9.1 | ) |  | (6.3 | ) |  | (4.7 | ) |  | (6.0 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (5.0 | ) |  | (2.0 | ) |  | (15.9 | ) |  | (14.2 | ) |  | (5.3 | ) |  | (0.8 | ) |  | (1.1 | ) |  | (0.5 | )
Adjustment of prior period taxes | (1.3 | ) |  | — |  |  | 0.2 |  |  | (3.6 | ) |  | 0.2 |  |  | 1.7 |  |  | (0.1 | ) |  | (0.3 | ) |  | — |
State apportionment change due to announced sale of RMT | — |  |  | 3.5 |  |  | — |  |  | — |  |  | 6.2 |  |  | — |  |  | — |  |  | 2.7 |  |  | — |
Wisconsin tax legislation | — |  |  | — |  |  | (4.6 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Other items, net | (1.8 | ) |  | (1.4 | ) |  | (0.9 | ) |  | (1.5 | ) |  | (1.6 | ) |  | (2.8 | ) |  | (0.9 | ) |  | (0.8 | ) |  | (0.1 | )
Overall income tax rate | 12.4 | % |  | 20.8 | % |  | 16.9 | % |  | (24.9 | %) |  | (15.2 | %) |  | (2.7 | %) |  | 32.9 | % |  | 36.3 | % |  | 33.4 | %
IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing the tax benefit riders. Refer to Note 2 for additional details on IPL’s tax benefit riders. Production tax credits - Alliant Energy, IPL and WPL earn production tax credits from the wind projects they own and operate. Production tax credits are based on the electricity generated by each wind project during the first 10 years of operation. Alliant Energy has three wind projects that are currently generating production tax credits: WPL’s 68 MW Cedar Ridge wind project, which began generating electricity in 2008; IPL’s 200 MW Whispering Willow - East wind project, which began generating electricity in 2009; and WPL’s 201 MW Bent Tree - Phase I wind project, which began generating electricity in 2010. Production tax credits (net of state tax impacts) resulting from these wind projects are included in the table below (in millions). Production tax credits for the Whispering Willow - East and Bent Tree - Phase I wind projects increased in 2013 primarily due to higher levels of electricity output generated by the wind projects.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Whispering Willow - East (IPL) |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Bent Tree - Phase I (WPL) | 12.5 |  |  | 9.3 |  |  | 9.3 |  |  | — |  |  | — |  |  | — |  |  | 12.5 |  |  | 9.3 |  |  | 9.3 |
Cedar Ridge (WPL) | 4.1 |  |  | 4.0 |  |  | 4.5 |  |  | — |  |  | — |  |  | — |  |  | 4.1 |  |  | 4.0 |  |  | 4.5 |
| 31.0 |  |  | 25.8 |  |  | 26.1 |  |  | 14.4 |  |  | 12.5 |  |  | 12.3 |  |  | 16.6 |  |  | 13.3 |  |  | 13.8 |
Deferral | — |  |  | (1.0 | ) |  | 1.0 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (1.0 | ) |  | 1.0 |
|  | $31.0 |  |  |  | $24.8 |  |  |  | $27.1 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $16.6 |  |  |  | $12.3 |  |  |  | $14.8 |
Effect of rate-making on property-related differences - Alliant Energy’s and IPL’s income tax expense and benefits are impacted by certain property-related differences at IPL for which deferred tax is not recognized in the income statement pursuant to Iowa rate-making principles. In 2012, the IRS audit to review the change in accounting method for allocation of mixed service costs and repairs expenditures was completed. Prior to 2012, tax expense and benefits at IPL related to mixed service costs and repairs expenditures book-to-tax differences were recorded in the tax benefit riders regulatory liability. Upon completion of the IRS audit, the tax expenses and benefits related to mixed service costs and repairs expenditures at IPL were recorded as a component of income tax expense beginning in 2012 pursuant to Iowa rate-making principles. The impact of the change in tax accounting methods for allocation of mixed service costs and repairs expenditures at IPL resulted in an increase in tax benefits for Alliant Energy and IPL in 2012. In 2013, the primary factor contributing to the increase in the current tax benefits recorded for the effect of rate-making on property-related differences was increased repairs expenditures and the equity component of AFUDC at IPL. Refer to Note 2 for additional details on IPL’s tax benefit riders. State apportionment change due to announced sale of RMT - Alliant Energy, IPL and WPL utilize state apportionment projections to record their deferred tax assets and liabilities each reporting period. Deferred tax assets and liabilities for temporary differences between the tax basis of assets and liabilities and the amounts reported in the consolidated financial statements are recorded utilizing currently enacted tax rates and estimates of future state apportionment rates expected to be in effect at the time the temporary differences reverse. These state apportionment projections are most significantly impacted by the estimated amount of revenues expected in the future from each state jurisdiction for Alliant Energy’s consolidated tax groups, including both its regulated and its non-regulated operations. In the first quarter of 2012, Alliant Energy, IPL and WPL recorded $15 million, $8 million and $7 million, respectively, of deferred income tax expense due to changes in state apportionment projections caused by the announced sale of Alliant Energy’s RMT business. Wisconsin tax legislation - In 2011, Act 32 was enacted. The most significant provision of Act 32 for Alliant Energy authorizes combined groups to share net operating loss carryforwards that were incurred by group members prior to January 1, 2009 and utilize these shared net operating losses over 20 years beginning after December 31, 2011. Based on this provision of Act 32, Alliant Energy anticipated its Wisconsin combined group would be able to fully utilize $368 million of Wisconsin net operating losses incurred by Alliant Energy and Resources prior to January 1, 2009 to offset future taxable income, and therefore, reversed previously recorded deferred tax asset valuation allowances related to state net operating loss carryforwards of $19 million in 2011. Deferred Tax Assets and Liabilities - The deferred income tax (assets) and liabilities included on Alliant Energy’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
Alliant Energy | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $2,316.3 |  |  | $2,316.3 |  |  |  | $— |  |  | $2,143.8 |  |  | $2,143.8 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Net operating losses carryforward - state | (35.3 | ) | — |  | (35.3 | ) |  | (46.8 | ) | — |  | (46.8 | )
Regulatory liability - IPL’s tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Federal credit carryforward | (167.8 | ) | — |  | (167.8 | ) |  | (133.8 | ) | — |  | (133.8 | )
Net operating losses carryforward - federal | (251.9 | ) | — |  | (251.9 | ) |  | (306.0 | ) | — |  | (306.0 | )
Other | (108.9 | ) | 210.7 |  | 101.8 |  |  | (113.7 | ) | 258.9 |  | 145.2 |
Subtotal | (671.7 | ) | 2,647.7 |  | 1,976.0 |  |  | (744.9 | ) | 2,507.0 |  | 1,762.1 |
Valuation allowances | — |  | — |  | — |  |  | 1.9 |  | — |  | 1.9 |
|  | ($671.7 | ) |  | $2,647.7 |  |  | $1,976.0 |  |  |  | ($743.0 | ) |  | $2,507.0 |  |  | $1,764.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($136.7 | ) |  |  | ($170.2 | )
Non-current deferred tax liabilities | 2,112.7 |  |  | 1,934.2 |
Total net deferred tax liabilities |  | $1,976.0 |  |  |  | $1,764.0 |
The deferred income tax (assets) and liabilities included on IPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
IPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $1,338.1 |  |  | $1,338.1 |  |  |  | $— |  |  | $1,243.9 |  |  | $1,243.9 |
Federal credit carryforward | (52.9 | ) | — |  | (52.9 | ) |  | (37.4 | ) | — |  | (37.4 | )
Regulatory liability - tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Net operating losses carryforward - federal | (111.3 | ) | — |  | (111.3 | ) |  | (131.0 | ) | — |  | (131.0 | )
Other | (64.0 | ) | 103.2 |  | 39.2 |  |  | (70.4 | ) | 147.5 |  | 77.1 |
|  | ($336.0 | ) |  | $1,441.3 |  |  | $1,105.3 |  |  |  | ($383.4 | ) |  | $1,391.4 |  |  | $1,008.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($87.7 | ) |  |  | ($79.3 | )
Non-current deferred tax liabilities | 1,193.0 |  |  | 1,087.3 |
Total net deferred tax liabilities |  | $1,105.3 |  |  |  | $1,008.0 |
The deferred income tax (assets) and liabilities included on WPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
WPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $859.1 |  |  | $859.1 |  |  |  | $— |  |  | $793.3 |  |  | $793.3 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Federal credit carryforward | (57.1 | ) | — |  | (57.1 | ) |  | (39.4 | ) | — |  | (39.4 | )
Net operating losses carryforward - federal | (106.9 | ) | — |  | (106.9 | ) |  | (142.2 | ) | — |  | (142.2 | )
Other | (37.6 | ) | 75.6 |  | 38.0 |  |  | (41.2 | ) | 83.7 |  | 42.5 |
|  | ($201.6 | ) |  | $1,055.4 |  |  | $853.8 |  |  |  | ($222.8 | ) |  | $981.3 |  |  | $758.5 |
| 2013 |  | 2012
Current deferred tax assets |  | ($43.3 | ) |  |  | ($85.6 | )
Non-current deferred tax liabilities | 897.1 |  |  | 844.1 |
Total net deferred tax liabilities |  | $853.8 |  |  |  | $758.5 |
Property - Property-related differences were primarily related to accelerated depreciation, including bonus depreciation. In January 2013, the ATR Act was enacted. The most significant provisions of the ATR Act for Alliant Energy, IPL and WPL are related to the extension of bonus depreciation deductions for certain expenditures for property that were incurred through December 31, 2013. Based on property expenditures incurred in 2013, Alliant Energy currently estimates its total bonus depreciation deductions to be claimed on its U.S. federal income tax return for calendar year 2013 will be approximately $130 million ($70 million for IPL and $45 million for WPL). Investment in ATC - WPL has a partial ownership interest in ATC, which has generated deferred tax liabilities primarily from tax depreciation deductions taken at ATC in excess of book depreciation. The increase in deferred tax liabilities in 2013 was primarily due to bonus depreciation deductions estimated at ATC. Carryforwards - At December 31, 2013, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $735 |  |  |  | $252 |  |  | 2029
State net operating losses | 686 |  |  | 35 |  |  | 2018
Federal tax credits | 170 |  |  | 168 |  |  | 2022
|  |  |  | $455 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $325 |  |  |  | $111 |  |  | 2029
State net operating losses | 189 |  |  | 10 |  |  | 2018
Federal tax credits | 54 |  |  | 53 |  |  | 2022
|  |  |  | $174 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $312 |  |  |  | $107 |  |  | 2029
State net operating losses | 99 |  |  | 5 |  |  | 2018
Federal tax credits | 58 |  |  | 57 |  |  | 2022
|  |  |  | $169 |  |  |
At December 31, 2013, Alliant Energy’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. At December 31, 2013, IPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 95% expiring after 2024. At December 31, 2013, WPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. Regulatory liability - tax benefit riders - Refer to Note 2 for discussion of regulatory liabilities associated with IPL’s tax benefit riders. Uncertain Tax Positions - A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Balance, January 1 |  | $0.7 |  |  |  | $23.5 |  |  |  | $66.7 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $33.0 |  |  |  | $0.7 |  |  |  | $12.6 |  |  |  | $33.7 |
Additions based on tax positions related to the current year | — |  |  | 0.7 |  |  | 0.7 |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.7 |  |  | 0.6 |
Reductions for tax positions of prior years (a) | (0.7 | ) |  | (23.5 | ) |  | (43.9 | ) |  | — |  |  | (10.9 | ) |  | (22.2 | ) |  | (0.7 | ) |  | (12.6 | ) |  | (21.7 | )
Balance, December 31 |  | $— |  |  |  | $0.7 |  |  |  | $23.5 |  |  |  | $— |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $0.7 |  |  |  | $12.6 |
(a) | In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repairs expenditures for electric distribution property.
At December 31, 2013, 2012 and 2011, there were no penalties accrued related to uncertain tax positions, and interest accrued and tax positions favorably impacting future effective tax rates for continuing operations were not material. As of December 31, 2013, Alliant Energy, IPL and WPL do not expect to have material changes to their unrecognized tax benefits during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations are as follows:
Major Jurisdiction |  | Alliant Energy |  | IPL |  | WPL
Consolidated federal income tax returns (a) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Consolidated Iowa income tax returns (b) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Wisconsin combined tax returns (c) |  | 2009 | - | 2012 |  | 2009 | - | 2012 |  | 2009 | - | 2012
(a) | 2010 through 2012 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 2010 through 2012 federal tax returns expires three years from their respective filing dates.
(b) | The statute of limitations for the 2010 through 2012 Iowa tax returns expires three years from their respective filing dates.
(c) | The statute of limitations for the 2009 through 2012 Wisconsin combined tax returns expires four years from their respective filing dates.
IPL [Member] |
Income Tax [Line Items] |
Income Taxes | INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $4.4 |  |  |  | ($29.3 | ) |  |  | $58.6 |  |  |  | $11.7 |  |  |  | ($7.7 | ) |  |  | $54.5 |  |  |  | ($5.7 | ) |  |  | $7.2 |  |  |  | ($4.3 | )
State | (3.6 | ) |  | 11.6 |  |  | 15.7 |  |  | (0.1 | ) |  | 9.1 |  |  | 20.0 |  |  | 6.0 |  |  | (0.9 | ) |  | (7.1 | )
IPL’s tax benefit riders | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 123.9 |  |  | 157.8 |  |  | 99.0 |  |  | 20.0 |  |  | 37.4 |  |  | (11.6 | ) |  | 92.7 |  |  | 81.1 |  |  | 111.3 |
State | 15.6 |  |  | 23.9 |  |  | (16.8 | ) |  | (0.8 | ) |  | 3.2 |  |  | (16.4 | ) |  | 11.8 |  |  | 20.3 |  |  | 19.0 |
Production tax credits | (31.0 | ) |  | (24.8 | ) |  | (27.1 | ) |  | (14.4 | ) |  | (12.5 | ) |  | (12.3 | ) |  | (16.6 | ) |  | (12.3 | ) |  | (14.8 | )
Investment tax credits | (1.6 | ) |  | (1.7 | ) |  | (1.8 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (1.0 | ) |  | (1.1 | ) |  | (1.2 | )
Provision recorded as a change in uncertain tax positions: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current | — |  |  | 8.0 |  |  | 16.3 |  |  | — |  |  | 8.1 |  |  | 16.6 |  |  | — |  |  | (0.1 | ) |  | (0.3 | )
Deferred | (0.4 | ) |  | (7.6 | ) |  | (38.3 | ) |  | — |  |  | (8.2 | ) |  | (17.6 | ) |  | (0.4 | ) |  | 0.6 |  |  | (20.7 | )
Provision recorded as a change in accrued interest | (0.5 | ) |  | (0.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.3 | ) |  | (0.3 | ) |  | 0.4 |  |  | (0.2 | ) |  | — |
|  | $53.9 |  |  |  | $89.4 |  |  |  | $69.2 |  |  |  | ($37.9 | ) |  |  | ($19.8 | ) |  |  | ($3.6 | ) |  |  | $87.2 |  |  |  | $94.6 |  |  |  | $81.9 |
Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.7 |  |  | 5.7 |  |  | 4.6 |  |  | 5.4 |  |  | 5.8 |  |  | 4.3 |  |  | 6.0 |  |  | 5.5 |  |  | 5.0 |
IPL’s tax benefit riders | (12.1 | ) |  | (11.2 | ) |  | (8.8 | ) |  | (34.8 | ) |  | (37.0 | ) |  | (26.5 | ) |  | — |  |  | — |  |  | — |
Production tax credits | (7.1 | ) |  | (5.8 | ) |  | (6.6 | ) |  | (9.5 | ) |  | (9.6 | ) |  | (9.1 | ) |  | (6.3 | ) |  | (4.7 | ) |  | (6.0 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (5.0 | ) |  | (2.0 | ) |  | (15.9 | ) |  | (14.2 | ) |  | (5.3 | ) |  | (0.8 | ) |  | (1.1 | ) |  | (0.5 | )
Adjustment of prior period taxes | (1.3 | ) |  | — |  |  | 0.2 |  |  | (3.6 | ) |  | 0.2 |  |  | 1.7 |  |  | (0.1 | ) |  | (0.3 | ) |  | — |
State apportionment change due to announced sale of RMT | — |  |  | 3.5 |  |  | — |  |  | — |  |  | 6.2 |  |  | — |  |  | — |  |  | 2.7 |  |  | — |
Wisconsin tax legislation | — |  |  | — |  |  | (4.6 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Other items, net | (1.8 | ) |  | (1.4 | ) |  | (0.9 | ) |  | (1.5 | ) |  | (1.6 | ) |  | (2.8 | ) |  | (0.9 | ) |  | (0.8 | ) |  | (0.1 | )
Overall income tax rate | 12.4 | % |  | 20.8 | % |  | 16.9 | % |  | (24.9 | %) |  | (15.2 | %) |  | (2.7 | %) |  | 32.9 | % |  | 36.3 | % |  | 33.4 | %
IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing the tax benefit riders. Refer to Note 2 for additional details on IPL’s tax benefit riders. Production tax credits - Alliant Energy, IPL and WPL earn production tax credits from the wind projects they own and operate. Production tax credits are based on the electricity generated by each wind project during the first 10 years of operation. Alliant Energy has three wind projects that are currently generating production tax credits: WPL’s 68 MW Cedar Ridge wind project, which began generating electricity in 2008; IPL’s 200 MW Whispering Willow - East wind project, which began generating electricity in 2009; and WPL’s 201 MW Bent Tree - Phase I wind project, which began generating electricity in 2010. Production tax credits (net of state tax impacts) resulting from these wind projects are included in the table below (in millions). Production tax credits for the Whispering Willow - East and Bent Tree - Phase I wind projects increased in 2013 primarily due to higher levels of electricity output generated by the wind projects.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Whispering Willow - East (IPL) |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Bent Tree - Phase I (WPL) | 12.5 |  |  | 9.3 |  |  | 9.3 |  |  | — |  |  | — |  |  | — |  |  | 12.5 |  |  | 9.3 |  |  | 9.3 |
Cedar Ridge (WPL) | 4.1 |  |  | 4.0 |  |  | 4.5 |  |  | — |  |  | — |  |  | — |  |  | 4.1 |  |  | 4.0 |  |  | 4.5 |
| 31.0 |  |  | 25.8 |  |  | 26.1 |  |  | 14.4 |  |  | 12.5 |  |  | 12.3 |  |  | 16.6 |  |  | 13.3 |  |  | 13.8 |
Deferral | — |  |  | (1.0 | ) |  | 1.0 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (1.0 | ) |  | 1.0 |
|  | $31.0 |  |  |  | $24.8 |  |  |  | $27.1 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $16.6 |  |  |  | $12.3 |  |  |  | $14.8 |
Effect of rate-making on property-related differences - Alliant Energy’s and IPL’s income tax expense and benefits are impacted by certain property-related differences at IPL for which deferred tax is not recognized in the income statement pursuant to Iowa rate-making principles. In 2012, the IRS audit to review the change in accounting method for allocation of mixed service costs and repairs expenditures was completed. Prior to 2012, tax expense and benefits at IPL related to mixed service costs and repairs expenditures book-to-tax differences were recorded in the tax benefit riders regulatory liability. Upon completion of the IRS audit, the tax expenses and benefits related to mixed service costs and repairs expenditures at IPL were recorded as a component of income tax expense beginning in 2012 pursuant to Iowa rate-making principles. The impact of the change in tax accounting methods for allocation of mixed service costs and repairs expenditures at IPL resulted in an increase in tax benefits for Alliant Energy and IPL in 2012. In 2013, the primary factor contributing to the increase in the current tax benefits recorded for the effect of rate-making on property-related differences was increased repairs expenditures and the equity component of AFUDC at IPL. Refer to Note 2 for additional details on IPL’s tax benefit riders. State apportionment change due to announced sale of RMT - Alliant Energy, IPL and WPL utilize state apportionment projections to record their deferred tax assets and liabilities each reporting period. Deferred tax assets and liabilities for temporary differences between the tax basis of assets and liabilities and the amounts reported in the consolidated financial statements are recorded utilizing currently enacted tax rates and estimates of future state apportionment rates expected to be in effect at the time the temporary differences reverse. These state apportionment projections are most significantly impacted by the estimated amount of revenues expected in the future from each state jurisdiction for Alliant Energy’s consolidated tax groups, including both its regulated and its non-regulated operations. In the first quarter of 2012, Alliant Energy, IPL and WPL recorded $15 million, $8 million and $7 million, respectively, of deferred income tax expense due to changes in state apportionment projections caused by the announced sale of Alliant Energy’s RMT business. Wisconsin tax legislation - In 2011, Act 32 was enacted. The most significant provision of Act 32 for Alliant Energy authorizes combined groups to share net operating loss carryforwards that were incurred by group members prior to January 1, 2009 and utilize these shared net operating losses over 20 years beginning after December 31, 2011. Based on this provision of Act 32, Alliant Energy anticipated its Wisconsin combined group would be able to fully utilize $368 million of Wisconsin net operating losses incurred by Alliant Energy and Resources prior to January 1, 2009 to offset future taxable income, and therefore, reversed previously recorded deferred tax asset valuation allowances related to state net operating loss carryforwards of $19 million in 2011. Deferred Tax Assets and Liabilities - The deferred income tax (assets) and liabilities included on Alliant Energy’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
Alliant Energy | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $2,316.3 |  |  | $2,316.3 |  |  |  | $— |  |  | $2,143.8 |  |  | $2,143.8 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Net operating losses carryforward - state | (35.3 | ) | — |  | (35.3 | ) |  | (46.8 | ) | — |  | (46.8 | )
Regulatory liability - IPL’s tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Federal credit carryforward | (167.8 | ) | — |  | (167.8 | ) |  | (133.8 | ) | — |  | (133.8 | )
Net operating losses carryforward - federal | (251.9 | ) | — |  | (251.9 | ) |  | (306.0 | ) | — |  | (306.0 | )
Other | (108.9 | ) | 210.7 |  | 101.8 |  |  | (113.7 | ) | 258.9 |  | 145.2 |
Subtotal | (671.7 | ) | 2,647.7 |  | 1,976.0 |  |  | (744.9 | ) | 2,507.0 |  | 1,762.1 |
Valuation allowances | — |  | — |  | — |  |  | 1.9 |  | — |  | 1.9 |
|  | ($671.7 | ) |  | $2,647.7 |  |  | $1,976.0 |  |  |  | ($743.0 | ) |  | $2,507.0 |  |  | $1,764.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($136.7 | ) |  |  | ($170.2 | )
Non-current deferred tax liabilities | 2,112.7 |  |  | 1,934.2 |
Total net deferred tax liabilities |  | $1,976.0 |  |  |  | $1,764.0 |
The deferred income tax (assets) and liabilities included on IPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
IPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $1,338.1 |  |  | $1,338.1 |  |  |  | $— |  |  | $1,243.9 |  |  | $1,243.9 |
Federal credit carryforward | (52.9 | ) | — |  | (52.9 | ) |  | (37.4 | ) | — |  | (37.4 | )
Regulatory liability - tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Net operating losses carryforward - federal | (111.3 | ) | — |  | (111.3 | ) |  | (131.0 | ) | — |  | (131.0 | )
Other | (64.0 | ) | 103.2 |  | 39.2 |  |  | (70.4 | ) | 147.5 |  | 77.1 |
|  | ($336.0 | ) |  | $1,441.3 |  |  | $1,105.3 |  |  |  | ($383.4 | ) |  | $1,391.4 |  |  | $1,008.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($87.7 | ) |  |  | ($79.3 | )
Non-current deferred tax liabilities | 1,193.0 |  |  | 1,087.3 |
Total net deferred tax liabilities |  | $1,105.3 |  |  |  | $1,008.0 |
The deferred income tax (assets) and liabilities included on WPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
WPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $859.1 |  |  | $859.1 |  |  |  | $— |  |  | $793.3 |  |  | $793.3 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Federal credit carryforward | (57.1 | ) | — |  | (57.1 | ) |  | (39.4 | ) | — |  | (39.4 | )
Net operating losses carryforward - federal | (106.9 | ) | — |  | (106.9 | ) |  | (142.2 | ) | — |  | (142.2 | )
Other | (37.6 | ) | 75.6 |  | 38.0 |  |  | (41.2 | ) | 83.7 |  | 42.5 |
|  | ($201.6 | ) |  | $1,055.4 |  |  | $853.8 |  |  |  | ($222.8 | ) |  | $981.3 |  |  | $758.5 |
| 2013 |  | 2012
Current deferred tax assets |  | ($43.3 | ) |  |  | ($85.6 | )
Non-current deferred tax liabilities | 897.1 |  |  | 844.1 |
Total net deferred tax liabilities |  | $853.8 |  |  |  | $758.5 |
Property - Property-related differences were primarily related to accelerated depreciation, including bonus depreciation. In January 2013, the ATR Act was enacted. The most significant provisions of the ATR Act for Alliant Energy, IPL and WPL are related to the extension of bonus depreciation deductions for certain expenditures for property that were incurred through December 31, 2013. Based on property expenditures incurred in 2013, Alliant Energy currently estimates its total bonus depreciation deductions to be claimed on its U.S. federal income tax return for calendar year 2013 will be approximately $130 million ($70 million for IPL and $45 million for WPL). Investment in ATC - WPL has a partial ownership interest in ATC, which has generated deferred tax liabilities primarily from tax depreciation deductions taken at ATC in excess of book depreciation. The increase in deferred tax liabilities in 2013 was primarily due to bonus depreciation deductions estimated at ATC. Carryforwards - At December 31, 2013, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $735 |  |  |  | $252 |  |  | 2029
State net operating losses | 686 |  |  | 35 |  |  | 2018
Federal tax credits | 170 |  |  | 168 |  |  | 2022
|  |  |  | $455 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $325 |  |  |  | $111 |  |  | 2029
State net operating losses | 189 |  |  | 10 |  |  | 2018
Federal tax credits | 54 |  |  | 53 |  |  | 2022
|  |  |  | $174 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $312 |  |  |  | $107 |  |  | 2029
State net operating losses | 99 |  |  | 5 |  |  | 2018
Federal tax credits | 58 |  |  | 57 |  |  | 2022
|  |  |  | $169 |  |  |
At December 31, 2013, Alliant Energy’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. At December 31, 2013, IPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 95% expiring after 2024. At December 31, 2013, WPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. Regulatory liability - tax benefit riders - Refer to Note 2 for discussion of regulatory liabilities associated with IPL’s tax benefit riders. Uncertain Tax Positions - A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Balance, January 1 |  | $0.7 |  |  |  | $23.5 |  |  |  | $66.7 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $33.0 |  |  |  | $0.7 |  |  |  | $12.6 |  |  |  | $33.7 |
Additions based on tax positions related to the current year | — |  |  | 0.7 |  |  | 0.7 |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.7 |  |  | 0.6 |
Reductions for tax positions of prior years (a) | (0.7 | ) |  | (23.5 | ) |  | (43.9 | ) |  | — |  |  | (10.9 | ) |  | (22.2 | ) |  | (0.7 | ) |  | (12.6 | ) |  | (21.7 | )
Balance, December 31 |  | $— |  |  |  | $0.7 |  |  |  | $23.5 |  |  |  | $— |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $0.7 |  |  |  | $12.6 |
(a) | In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repairs expenditures for electric distribution property.
At December 31, 2013, 2012 and 2011, there were no penalties accrued related to uncertain tax positions, and interest accrued and tax positions favorably impacting future effective tax rates for continuing operations were not material. As of December 31, 2013, Alliant Energy, IPL and WPL do not expect to have material changes to their unrecognized tax benefits during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations are as follows:
Major Jurisdiction |  | Alliant Energy |  | IPL |  | WPL
Consolidated federal income tax returns (a) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Consolidated Iowa income tax returns (b) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Wisconsin combined tax returns (c) |  | 2009 | - | 2012 |  | 2009 | - | 2012 |  | 2009 | - | 2012
(a) | 2010 through 2012 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 2010 through 2012 federal tax returns expires three years from their respective filing dates.
(b) | The statute of limitations for the 2010 through 2012 Iowa tax returns expires three years from their respective filing dates.
(c) | The statute of limitations for the 2009 through 2012 Wisconsin combined tax returns expires four years from their respective filing dates.
WPL [Member] |
Income Tax [Line Items] |
Income Taxes | INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $4.4 |  |  |  | ($29.3 | ) |  |  | $58.6 |  |  |  | $11.7 |  |  |  | ($7.7 | ) |  |  | $54.5 |  |  |  | ($5.7 | ) |  |  | $7.2 |  |  |  | ($4.3 | )
State | (3.6 | ) |  | 11.6 |  |  | 15.7 |  |  | (0.1 | ) |  | 9.1 |  |  | 20.0 |  |  | 6.0 |  |  | (0.9 | ) |  | (7.1 | )
IPL’s tax benefit riders | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | (52.9 | ) |  | (48.3 | ) |  | (35.9 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 123.9 |  |  | 157.8 |  |  | 99.0 |  |  | 20.0 |  |  | 37.4 |  |  | (11.6 | ) |  | 92.7 |  |  | 81.1 |  |  | 111.3 |
State | 15.6 |  |  | 23.9 |  |  | (16.8 | ) |  | (0.8 | ) |  | 3.2 |  |  | (16.4 | ) |  | 11.8 |  |  | 20.3 |  |  | 19.0 |
Production tax credits | (31.0 | ) |  | (24.8 | ) |  | (27.1 | ) |  | (14.4 | ) |  | (12.5 | ) |  | (12.3 | ) |  | (16.6 | ) |  | (12.3 | ) |  | (14.8 | )
Investment tax credits | (1.6 | ) |  | (1.7 | ) |  | (1.8 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (1.0 | ) |  | (1.1 | ) |  | (1.2 | )
Provision recorded as a change in uncertain tax positions: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current | — |  |  | 8.0 |  |  | 16.3 |  |  | — |  |  | 8.1 |  |  | 16.6 |  |  | — |  |  | (0.1 | ) |  | (0.3 | )
Deferred | (0.4 | ) |  | (7.6 | ) |  | (38.3 | ) |  | — |  |  | (8.2 | ) |  | (17.6 | ) |  | (0.4 | ) |  | 0.6 |  |  | (20.7 | )
Provision recorded as a change in accrued interest | (0.5 | ) |  | (0.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.3 | ) |  | (0.3 | ) |  | 0.4 |  |  | (0.2 | ) |  | — |
|  | $53.9 |  |  |  | $89.4 |  |  |  | $69.2 |  |  |  | ($37.9 | ) |  |  | ($19.8 | ) |  |  | ($3.6 | ) |  |  | $87.2 |  |  |  | $94.6 |  |  |  | $81.9 |
Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.7 |  |  | 5.7 |  |  | 4.6 |  |  | 5.4 |  |  | 5.8 |  |  | 4.3 |  |  | 6.0 |  |  | 5.5 |  |  | 5.0 |
IPL’s tax benefit riders | (12.1 | ) |  | (11.2 | ) |  | (8.8 | ) |  | (34.8 | ) |  | (37.0 | ) |  | (26.5 | ) |  | — |  |  | — |  |  | — |
Production tax credits | (7.1 | ) |  | (5.8 | ) |  | (6.6 | ) |  | (9.5 | ) |  | (9.6 | ) |  | (9.1 | ) |  | (6.3 | ) |  | (4.7 | ) |  | (6.0 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (5.0 | ) |  | (2.0 | ) |  | (15.9 | ) |  | (14.2 | ) |  | (5.3 | ) |  | (0.8 | ) |  | (1.1 | ) |  | (0.5 | )
Adjustment of prior period taxes | (1.3 | ) |  | — |  |  | 0.2 |  |  | (3.6 | ) |  | 0.2 |  |  | 1.7 |  |  | (0.1 | ) |  | (0.3 | ) |  | — |
State apportionment change due to announced sale of RMT | — |  |  | 3.5 |  |  | — |  |  | — |  |  | 6.2 |  |  | — |  |  | — |  |  | 2.7 |  |  | — |
Wisconsin tax legislation | — |  |  | — |  |  | (4.6 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Other items, net | (1.8 | ) |  | (1.4 | ) |  | (0.9 | ) |  | (1.5 | ) |  | (1.6 | ) |  | (2.8 | ) |  | (0.9 | ) |  | (0.8 | ) |  | (0.1 | )
Overall income tax rate | 12.4 | % |  | 20.8 | % |  | 16.9 | % |  | (24.9 | %) |  | (15.2 | %) |  | (2.7 | %) |  | 32.9 | % |  | 36.3 | % |  | 33.4 | %
IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing the tax benefit riders. Refer to Note 2 for additional details on IPL’s tax benefit riders. Production tax credits - Alliant Energy, IPL and WPL earn production tax credits from the wind projects they own and operate. Production tax credits are based on the electricity generated by each wind project during the first 10 years of operation. Alliant Energy has three wind projects that are currently generating production tax credits: WPL’s 68 MW Cedar Ridge wind project, which began generating electricity in 2008; IPL’s 200 MW Whispering Willow - East wind project, which began generating electricity in 2009; and WPL’s 201 MW Bent Tree - Phase I wind project, which began generating electricity in 2010. Production tax credits (net of state tax impacts) resulting from these wind projects are included in the table below (in millions). Production tax credits for the Whispering Willow - East and Bent Tree - Phase I wind projects increased in 2013 primarily due to higher levels of electricity output generated by the wind projects.
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Whispering Willow - East (IPL) |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Bent Tree - Phase I (WPL) | 12.5 |  |  | 9.3 |  |  | 9.3 |  |  | — |  |  | — |  |  | — |  |  | 12.5 |  |  | 9.3 |  |  | 9.3 |
Cedar Ridge (WPL) | 4.1 |  |  | 4.0 |  |  | 4.5 |  |  | — |  |  | — |  |  | — |  |  | 4.1 |  |  | 4.0 |  |  | 4.5 |
| 31.0 |  |  | 25.8 |  |  | 26.1 |  |  | 14.4 |  |  | 12.5 |  |  | 12.3 |  |  | 16.6 |  |  | 13.3 |  |  | 13.8 |
Deferral | — |  |  | (1.0 | ) |  | 1.0 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (1.0 | ) |  | 1.0 |
|  | $31.0 |  |  |  | $24.8 |  |  |  | $27.1 |  |  |  | $14.4 |  |  |  | $12.5 |  |  |  | $12.3 |  |  |  | $16.6 |  |  |  | $12.3 |  |  |  | $14.8 |
Effect of rate-making on property-related differences - Alliant Energy’s and IPL’s income tax expense and benefits are impacted by certain property-related differences at IPL for which deferred tax is not recognized in the income statement pursuant to Iowa rate-making principles. In 2012, the IRS audit to review the change in accounting method for allocation of mixed service costs and repairs expenditures was completed. Prior to 2012, tax expense and benefits at IPL related to mixed service costs and repairs expenditures book-to-tax differences were recorded in the tax benefit riders regulatory liability. Upon completion of the IRS audit, the tax expenses and benefits related to mixed service costs and repairs expenditures at IPL were recorded as a component of income tax expense beginning in 2012 pursuant to Iowa rate-making principles. The impact of the change in tax accounting methods for allocation of mixed service costs and repairs expenditures at IPL resulted in an increase in tax benefits for Alliant Energy and IPL in 2012. In 2013, the primary factor contributing to the increase in the current tax benefits recorded for the effect of rate-making on property-related differences was increased repairs expenditures and the equity component of AFUDC at IPL. Refer to Note 2 for additional details on IPL’s tax benefit riders. State apportionment change due to announced sale of RMT - Alliant Energy, IPL and WPL utilize state apportionment projections to record their deferred tax assets and liabilities each reporting period. Deferred tax assets and liabilities for temporary differences between the tax basis of assets and liabilities and the amounts reported in the consolidated financial statements are recorded utilizing currently enacted tax rates and estimates of future state apportionment rates expected to be in effect at the time the temporary differences reverse. These state apportionment projections are most significantly impacted by the estimated amount of revenues expected in the future from each state jurisdiction for Alliant Energy’s consolidated tax groups, including both its regulated and its non-regulated operations. In the first quarter of 2012, Alliant Energy, IPL and WPL recorded $15 million, $8 million and $7 million, respectively, of deferred income tax expense due to changes in state apportionment projections caused by the announced sale of Alliant Energy’s RMT business. Wisconsin tax legislation - In 2011, Act 32 was enacted. The most significant provision of Act 32 for Alliant Energy authorizes combined groups to share net operating loss carryforwards that were incurred by group members prior to January 1, 2009 and utilize these shared net operating losses over 20 years beginning after December 31, 2011. Based on this provision of Act 32, Alliant Energy anticipated its Wisconsin combined group would be able to fully utilize $368 million of Wisconsin net operating losses incurred by Alliant Energy and Resources prior to January 1, 2009 to offset future taxable income, and therefore, reversed previously recorded deferred tax asset valuation allowances related to state net operating loss carryforwards of $19 million in 2011. Deferred Tax Assets and Liabilities - The deferred income tax (assets) and liabilities included on Alliant Energy’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
Alliant Energy | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $2,316.3 |  |  | $2,316.3 |  |  |  | $— |  |  | $2,143.8 |  |  | $2,143.8 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Net operating losses carryforward - state | (35.3 | ) | — |  | (35.3 | ) |  | (46.8 | ) | — |  | (46.8 | )
Regulatory liability - IPL’s tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Federal credit carryforward | (167.8 | ) | — |  | (167.8 | ) |  | (133.8 | ) | — |  | (133.8 | )
Net operating losses carryforward - federal | (251.9 | ) | — |  | (251.9 | ) |  | (306.0 | ) | — |  | (306.0 | )
Other | (108.9 | ) | 210.7 |  | 101.8 |  |  | (113.7 | ) | 258.9 |  | 145.2 |
Subtotal | (671.7 | ) | 2,647.7 |  | 1,976.0 |  |  | (744.9 | ) | 2,507.0 |  | 1,762.1 |
Valuation allowances | — |  | — |  | — |  |  | 1.9 |  | — |  | 1.9 |
|  | ($671.7 | ) |  | $2,647.7 |  |  | $1,976.0 |  |  |  | ($743.0 | ) |  | $2,507.0 |  |  | $1,764.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($136.7 | ) |  |  | ($170.2 | )
Non-current deferred tax liabilities | 2,112.7 |  |  | 1,934.2 |
Total net deferred tax liabilities |  | $1,976.0 |  |  |  | $1,764.0 |
The deferred income tax (assets) and liabilities included on IPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
IPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $1,338.1 |  |  | $1,338.1 |  |  |  | $— |  |  | $1,243.9 |  |  | $1,243.9 |
Federal credit carryforward | (52.9 | ) | — |  | (52.9 | ) |  | (37.4 | ) | — |  | (37.4 | )
Regulatory liability - tax benefit riders | (107.8 | ) | — |  | (107.8 | ) |  | (144.6 | ) | — |  | (144.6 | )
Net operating losses carryforward - federal | (111.3 | ) | — |  | (111.3 | ) |  | (131.0 | ) | — |  | (131.0 | )
Other | (64.0 | ) | 103.2 |  | 39.2 |  |  | (70.4 | ) | 147.5 |  | 77.1 |
|  | ($336.0 | ) |  | $1,441.3 |  |  | $1,105.3 |  |  |  | ($383.4 | ) |  | $1,391.4 |  |  | $1,008.0 |
| 2013 |  | 2012
Current deferred tax assets |  | ($87.7 | ) |  |  | ($79.3 | )
Non-current deferred tax liabilities | 1,193.0 |  |  | 1,087.3 |
Total net deferred tax liabilities |  | $1,105.3 |  |  |  | $1,008.0 |
The deferred income tax (assets) and liabilities included on WPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):
| 2013 |  | 2012
| Deferred | Deferred Tax |  |  | Deferred | Deferred Tax |
WPL | Tax Assets | Liabilities | Net |  | Tax Assets | Liabilities | Net
Property |  | $— |  |  | $859.1 |  |  | $859.1 |  |  |  | $— |  |  | $793.3 |  |  | $793.3 |
Investment in ATC | — |  | 120.7 |  | 120.7 |  |  | — |  | 104.3 |  | 104.3 |
Federal credit carryforward | (57.1 | ) | — |  | (57.1 | ) |  | (39.4 | ) | — |  | (39.4 | )
Net operating losses carryforward - federal | (106.9 | ) | — |  | (106.9 | ) |  | (142.2 | ) | — |  | (142.2 | )
Other | (37.6 | ) | 75.6 |  | 38.0 |  |  | (41.2 | ) | 83.7 |  | 42.5 |
|  | ($201.6 | ) |  | $1,055.4 |  |  | $853.8 |  |  |  | ($222.8 | ) |  | $981.3 |  |  | $758.5 |
| 2013 |  | 2012
Current deferred tax assets |  | ($43.3 | ) |  |  | ($85.6 | )
Non-current deferred tax liabilities | 897.1 |  |  | 844.1 |
Total net deferred tax liabilities |  | $853.8 |  |  |  | $758.5 |
Property - Property-related differences were primarily related to accelerated depreciation, including bonus depreciation. In January 2013, the ATR Act was enacted. The most significant provisions of the ATR Act for Alliant Energy, IPL and WPL are related to the extension of bonus depreciation deductions for certain expenditures for property that were incurred through December 31, 2013. Based on property expenditures incurred in 2013, Alliant Energy currently estimates its total bonus depreciation deductions to be claimed on its U.S. federal income tax return for calendar year 2013 will be approximately $130 million ($70 million for IPL and $45 million for WPL). Investment in ATC - WPL has a partial ownership interest in ATC, which has generated deferred tax liabilities primarily from tax depreciation deductions taken at ATC in excess of book depreciation. The increase in deferred tax liabilities in 2013 was primarily due to bonus depreciation deductions estimated at ATC. Carryforwards - At December 31, 2013, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $735 |  |  |  | $252 |  |  | 2029
State net operating losses | 686 |  |  | 35 |  |  | 2018
Federal tax credits | 170 |  |  | 168 |  |  | 2022
|  |  |  | $455 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $325 |  |  |  | $111 |  |  | 2029
State net operating losses | 189 |  |  | 10 |  |  | 2018
Federal tax credits | 54 |  |  | 53 |  |  | 2022
|  |  |  | $174 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $312 |  |  |  | $107 |  |  | 2029
State net operating losses | 99 |  |  | 5 |  |  | 2018
Federal tax credits | 58 |  |  | 57 |  |  | 2022
|  |  |  | $169 |  |  |
At December 31, 2013, Alliant Energy’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. At December 31, 2013, IPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 95% expiring after 2024. At December 31, 2013, WPL’s state net operating losses carryforwards had expiration dates ranging from 2018 to 2031 with 98% expiring after 2024. Regulatory liability - tax benefit riders - Refer to Note 2 for discussion of regulatory liabilities associated with IPL’s tax benefit riders. Uncertain Tax Positions - A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011 |  | 2013 |  | 2012 |  | 2011
Balance, January 1 |  | $0.7 |  |  |  | $23.5 |  |  |  | $66.7 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $33.0 |  |  |  | $0.7 |  |  |  | $12.6 |  |  |  | $33.7 |
Additions based on tax positions related to the current year | — |  |  | 0.7 |  |  | 0.7 |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.7 |  |  | 0.6 |
Reductions for tax positions of prior years (a) | (0.7 | ) |  | (23.5 | ) |  | (43.9 | ) |  | — |  |  | (10.9 | ) |  | (22.2 | ) |  | (0.7 | ) |  | (12.6 | ) |  | (21.7 | )
Balance, December 31 |  | $— |  |  |  | $0.7 |  |  |  | $23.5 |  |  |  | $— |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $0.7 |  |  |  | $12.6 |
(a) | In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repairs expenditures for electric distribution property.
At December 31, 2013, 2012 and 2011, there were no penalties accrued related to uncertain tax positions, and interest accrued and tax positions favorably impacting future effective tax rates for continuing operations were not material. As of December 31, 2013, Alliant Energy, IPL and WPL do not expect to have material changes to their unrecognized tax benefits during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations are as follows:
Major Jurisdiction |  | Alliant Energy |  | IPL |  | WPL
Consolidated federal income tax returns (a) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Consolidated Iowa income tax returns (b) |  | 2010 | - | 2012 |  | 2010 | - | 2012 |  | 2010 | - | 2012
Wisconsin combined tax returns (c) |  | 2009 | - | 2012 |  | 2009 | - | 2012 |  | 2009 | - | 2012
(a) | 2010 through 2012 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 2010 through 2012 federal tax returns expires three years from their respective filing dates.
(b) | The statute of limitations for the 2010 through 2012 Iowa tax returns expires three years from their respective filing dates.
(c) | The statute of limitations for the 2009 through 2012 Wisconsin combined tax returns expires four years from their respective filing dates.

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