Form 11-K 12/31/06

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

 

FORM 11-K

 

 

x

ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES

 

EXCHANGE ACT OF 1934

 

 

 

For the fiscal year ended December 31, 2006

 

or

 

o

TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES

 

EXCHANGE ACT OF 1934

 

 

 

For the transition period from

_____________ to _____________

 

 

Commission File Number: 1-9894

 

 

A.

Full title of the plan and address of the plan, if different from that of the issuer named below:

 

 

ALLIANT ENERGY CORPORATION 401(k) SAVINGS PLAN

 

 

B.

Name of issuer of the securities held pursuant to the plan and the address of its principal

executive office:

 

ALLIANT ENERGY CORPORATION

4902 North Biltmore Lane

Madison, Wisconsin 53718

 

 

 

 

 

 

REQUIRED INFORMATION

 

The following financial statements and schedules of the Alliant Energy Corporation 401(k) Savings Plan, prepared in accordance with the financial reporting requirements of the Employee Retirement Income Security Act of 1974, as amended, are filed herewith.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page 1 of 22 pages

Exhibit Index is on page 21

 

1

ALLIANT ENERGY CORPORATION

 

401(k) SAVINGS PLAN

 

FINANCIAL STATEMENTS AS OF DECEMBER 31, 2006 AND 2005

 

AND FOR THE YEAR ENDED DECEMBER 31, 2006,

 

SUPPLEMENTAL SCHEDULES AS OF AND FOR THE YEAR ENDED DECEMBER 31, 2006, AND

 

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

 

2

ALLIANT ENERGY CORPORATION

 

401(k) SAVINGS PLAN

 

 

TABLE OF CONTENTS

 

 

Page No.

 

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

4

 

FINANCIAL STATEMENTS

 

 

Statements of Net Assets Available for Benefits

 

 

as of December 31, 2006 and 2005

5

 

 

Statement of Changes in Net Assets Available for Benefits

 

 

for the Year Ended December 31, 2006

6

 

NOTES TO FINANCIAL STATEMENTS

7-12

 

SUPPLEMENTAL SCHEDULES

 

 

Form 5500, Schedule H, Part IV, line 4i - Schedule of Assets (Held at End of Year)

 

 

as of December 31, 2006

13-17

 

 

Form 5500, Schedule H, Part IV, line 4i - Schedule of Assets (Acquired and Disposed

 

 

of Within Year) for the Year Ended December 31, 2006

18

 

 

Form 5500, Schedule H, Part IV, line 4j - Schedule of Reportable Transactions

 

 

for the Year Ended December 31, 2006

19

 

SIGNATURES

20

 

EXHIBIT INDEX

21

 

 

Consent of Independent Registered Public Accounting Firm

22

 

 

 

3

Report of Independent Registered Public Accounting Firm

 

To the Total Compensation Committee and Participants of the Alliant Energy Corporation 401(k) Savings Plan:

 

We have audited the accompanying statements of net assets available for benefits of Alliant Energy Corporation 401(k) Savings Plan (the “Plan”) as of December 31, 2006 and 2005, and the related statement of changes in net assets available for benefits for the year ended December 31, 2006. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

 

We conducted our audits in accordance with standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. The Plan is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. Our audits included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Plan’s internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

 

In our opinion, such financial statements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2006 and 2005, and the changes in net assets available for benefits for the year ended December 31, 2006 in conformity with accounting principles generally accepted in the United States of America.

 

Our audits were conducted for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedules of (1) assets (held at end of year) as of December 31, 2006, (2) assets (acquired and disposed of within year) for the year ended December 31, 2006, and (3) reportable transactions for the year ended December 31, 2006, are presented for the purpose of additional analysis and are not a required part of the basic financial statements, but are supplementary information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. These schedules are the responsibility of the Plan’s management. Such schedules have been subjected to the auditing procedures applied in our audit of the basic 2006 financial statements and, in our opinion, are fairly stated in all material respects when considered in relation to the basic financial statements taken as a whole.

 

/s/ Deloitte & Touche LLP

 

Milwaukee, Wisconsin

June 22, 2007

4

ALLIANT ENERGY CORPORATION

401(k) SAVINGS PLAN

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS

        December 31,
        2006       2005
 
    Investment income receivable $220,277  $1,916,893 
    Contributions receivable --  1,256,949 
 
        Total receivables 220,277  3,173,842 
 
    Investments, other than participant promissory notes (Refer to Notes 7 and 8) 577,699,020  486,711,444 
    Participant promissory notes 9,305,638  8,837,772 
 
        Total investments 587,004,658  495,549,216 
 
Net assets available for benefits at fair value 587,224,935  498,723,058 
     
    Adjustments from fair value to contract value for fully benefit-
      responsive investment contracts (Refer to Note 2) 435,698  518,125 
 
Net assets available for benefits $587,660,633  $499,241,183 
 

The accompanying Notes to Financial Statements are an integral part of these statements.

5

ALLIANT ENERGY CORPORATION

401(k) SAVINGS PLAN

STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

For the Year Ended December 31, 2006

Net assets available for benefits - beginning of year   $499,241,183  
       
Contributions: 
     Cash contributions from employees  26,431,405  
     Employer contributions: 
         Cash for purchase of Alliant Energy Corporation common stock  7,562,464  
         Cash  535,990  
     Rollovers from other qualified plans  397,501  
       
Investment income:  
     Net appreciation in fair value of investments (Refer to Note 7)   64,838,281  
     Interest and dividends  26,247,210  
       
Distributions to participants   (37,593,401 )
 
   Net increase   88,419,450  
 
 Net assets available for benefits - end of year   $587,660,633  
 

The accompanying Notes to Financial Statements are an integral part of this statement.

6

ALLIANT ENERGY CORPORATION

401(k) SAVINGS PLAN

 

NOTES TO FINANCIAL STATEMENTS

FOR THE YEAR ENDED DECEMBER 31, 2006

 

Note 1.

Description of the Plan

 

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 (ERISA). 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 Total Compensation 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 days of service. Part-time employees customarily scheduled to work less than half-time may participate after 12 months of service during which he or she has earned at least 1,000 paid hours.

 

An Employee Stock Ownership Plan (ESOP) is in place within the Plan. Under these provisions, participants have the option to elect to receive cash 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. Also, the Company is eligible for the dividend deduction provisions of Section 404(k) of the Code for Company common stock held in the ESOP.

 

Effective Jan. 1, 2006, the Company made changes to the Plan for newly hired non-bargaining employees and all Alliant Energy Resources, Inc. parent company (Resources) and Cedar Rapids and Iowa City Railway Company (CRANDIC) employees. For all other non-bargaining employees, the following changes will go into effect on Aug. 1, 2008. The changes include the Company providing 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 base pay as follows:

 

 

 

Company

Age plus Years of Service

 

Contribution

< 49

 

4%

50 - 69

 

5%

70+

 

6%

                

For all other non-bargaining and bargaining employees, the Company provides matching contributions of $0.50 for each $1 contributed by the participant up to the first 6% of each respective participant’s eligible compensation.

 

 

Employee contribution limits for 2006 were as follows:

 

Eligible employee annual contribution limit as a percentage of compensation

50%

Maximum annual contribution limit*

$15,000

*Participants who were at least age 50 by Dec. 31, 2006 were eligible to make additional catch-up contributions of up to $5,000 in 2006. These additional catch-up contributions were not eligible for any Company match.

7

 

Company contributions are invested in the Alliant Energy Corporation Common Stock Fund, except for contributions for newly hired non-bargaining employees and all Resources and CRANDIC employees beginning Jan. 1, 2006. These exceptions are invested at each participant’s discretion. Effective Oct. 2, 2006, the Plan enhanced its existing diversification provisions by allowing participants with at least three years of service to transfer their Company matching contributions invested in the Alliant Energy Corporation Company Stock Fund to any other investment fund. Previously, Company matching contributions invested in the Alliant Energy Corporation Company Stock Fund could not be transferred to any other investment fund, except for certain participants during the 30-day period immediately prior to retirement and participants age 55 with 10 years of service were eligible to diversify up to 100% of their ESOP account to one or more of the investment options.

 

During 2005, Resources and CRANDIC employees were eligible for a “discretionary” Company contribution of $0.50 for every $1 contributed by the participant up to a maximum of the first 6% of each respective participant’s eligible compensation in addition to the “basic” Company contribution. The “discretionary” contribution for both Resources and CRANDIC employees was based on achieving specified goals and was typically determined and paid during the first quarter of the following year. The “discretionary” Company contributions for 2005 were $198,808. Effective Jan. 1, 2006 this “discretionary” contribution is no longer available.

 

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 6% of compensation during the Plan year and did not receive a Company matching contribution equal to 3% of compensation or for those eligible for a matching contribution equal to 4% of compensation who contributed 8% of compensation during the Plan year. The amount of the “additional” Company contribution is the difference between 3% of compensation or 4% of compensation for certain employees during the Plan year and the amount of Company matching contributions previously received during the Plan year.

 

Participants are immediately vested in their respective employee and employer contributions. Participants may subsequently redesignate 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.

 

Contributions under the Plan are held and invested, until distribution, in a Trust Fund maintained by Wachovia Bank, National Association (the Trustee), as successor to Ameriprise Trust Company. On June 1, 2006, Wachovia Bank, National Association acquired Ameriprise Trust Company’s recordkeeping business.

 

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 5.0% to 10.5% at both Dec. 31, 2006 and 2005. Principal and interest are repaid bi-weekly through employee payroll deductions.

 

Note 2.

Summary of Significant Accounting Policies

 

(a) Basis of Accounting - The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP).

 

(b) Adoption of New Accounting Guidance - In 2006, the Plan adopted Financial Accounting Standards Board Staff Position, FSP AAG INV-1 and SOP 94-4-1, “Reporting of Fully Benefit-Responsive Contracts Held by Certain Investment Companies Subject to the AICPA Investment Company Guide and Defined-Contribution Health and Welfare and Pension Plans” (FSP) and retrospectively adjusted the statement of net assets available for benefits as of Dec. 31, 2005 to adopt this new accounting standard. As required by the FSP, the statements of net assets available for benefits present investments at fair value as well as an additional line item showing an adjustment of fully benefit-responsive contracts from fair value to contract value. The statement of changes in net assets available for benefits is presented on a contract value basis and was not affected by the adoption of the FSP. The adoption of the FSP did not impact the amount of net assets available for benefits at Dec. 31, 2005.

8

 

(c) Valuation of Investments and Income Recognition - The Plan’s investments are stated at fair value. All Guaranteed Investment Contracts (GIC’s) held by the Plan are fully benefit-responsive. The contract value of all GIC investments was $48,954,702 and $47,341,620 at Dec. 31, 2006 and 2005, respectively. The approximate fair value of these investments was $48,570,228 and $46,887,620 at Dec. 31, 2006 and 2005, respectively, based on the discounted cash flows valuation method. The weighted average yields for the GIC’s based on annualized earnings on Dec. 31, 2006 and 2005, were 5.47% and 5.06%, respectively. The weighted average yields for the GIC’s based on the interest rate credited to participants on Dec. 31, 2006 and 2005, were 5.11% and 4.33%, respectively. Participant loans are carried at unpaid principal balances due, which approximates fair value. All other Plan investments are carried at fair value as determined by quoted market prices, except for the RiverSource Trust Income Fund I. The RiverSource Trust Income Fund I is a common collective trust fund, which includes investments in fully benefit-responsive GIC’s and is reported at fair value at Dec. 31, 2006 and 2005, as determined by Ameriprise Trust Company. Interest income is accrued when earned. Dividend income is recorded on the ex-dividend date. Investment transactions are recorded on the trade date.

 

(d) Net Appreciation in Fair Value of Investments - Net realized and unrealized appreciation is recorded in the accompanying statement of changes in net assets available for benefits as “Net appreciation in fair value of investments.”

 

(e) Payment of Benefits - Benefit payments to participants are recorded when paid.

 

(f) Expenses - Investment management and recordkeeping fees are paid from investment earnings prior to crediting earnings to the individual participant account balances. Most other Plan administrative expenses are absorbed by the Company. Expenses incurred in maintaining Self-Managed Brokerage Accounts are the responsibility of the respective Plan participants.

 

(g) 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.

 

(h) Risk and Uncertainties - The Plan invests in various investments, including common investment funds, mutual funds, common stock of the Company and investment contracts. The Plan also offers a Self-Managed Brokerage Account option which allows participants to invest in a wide range of mutual funds. Investments, in general, are exposed to various risks, such as interest rate, credit, and overall market volatility. 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.

 

Note 3.

Tax Status

 

The Internal Revenue Service has determined and informed the Company by a letter dated Aug. 25, 2003, 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. However, 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.

 

9

Note 4.

Plan Termination Provisions

 

Upon termination of the Plan in its entirety, each participant is entitled to receive, in accordance with the terms of the Plan, the entire balance in their account. The Company has no intention to terminate the Plan.

 

Note 5.

Withdrawals and Distributions

 

Withdrawals from participants’ account balances are allowed when participants who are actively employed reach age 70-1/2 (or age 59-1/2 for certain participants). Withdrawals are also allowed due to special “hardship” circumstances. 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. If a withdrawing participant’s account balance exceeds $1,000 but 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 at the Trustee. If a withdrawing participant’s account balance exceeds $5,000, the participant may elect to defer payment until he or she is age 70-1/2. Distributions can be either in the form of a lump sum or substantially equal 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 Dec. 31, 2006 and 2005 were $227,307 and $59,982, respectively. Distributions payable are not included within net assets available for benefits in the accompanying financial statements, however, they are recorded as liabilities in the Plan’s Form 5500 (refer to Note 10).

 

Note 6.

Derivative Financial Instruments

 

The Plan did not invest in any material derivative financial instruments during 2006 and 2005.

 

Note 7.

Other Investment Information

 

Investments held which were greater than 5% of the Plan's net assets available for benefits as of Dec. 31 were as follows:

 

 

2006

 

2005

Alliant Energy Corporation Common Stock*

$137,820,283

 

$107,427,885

(non-participant directed: $817,826 (21,654 shares) and

 

 

 

    $68,338,101 (2,437,165 shares), respectively)

 

 

 

(participant directed: $137,002,457 (3,627,526 shares) and $39,089,784

 

 

 

    (1,394,072 shares), respectively)

 

 

 

American Funds Growth Fund of America, 2,716,565 and 2,660,335

 

 

 

shares, respectively

89,293,482

 

82,097,953

RiverSource Trust Equity Index Fund III*, 1,959,874 and 2,209,051

 

 

 

shares, respectively

78,104,900

 

76,095,171

Dodge & Cox Stock Fund, 367,953 and 300,943 shares, respectively

56,466,030

 

41,295,339

American Funds EuroPacific Growth Fund, 913,251 and 741,088

 

 

 

shares, respectively

41,991,279

 

30,110,419

PIMCO Total Return Fund, 3,024,733 and 2,780,718 shares, respectively

31,396,730

 

29,197,536

* Represents party known to be a party-in-interest to the Plan.

 

10

During 2006, the Plan’s investments, including gains and losses on investments acquired and disposed of, as well as held during the year, appreciated (depreciated) in value as follows:

 

Alliant Energy Corporation Common Stock*

$36,888,292

RiverSource Trust Equity Index Fund III*

10,957,207

American Funds Growth Fund of America

5,347,150

Dodge & Cox Stock Fund

5,117,418

American Funds EuroPacific Growth Fund

4,212,352

Buffalo Small Cap Fund

1,235,350

State Street Global Advisors S&P Midcap Index Fund

1,220,670

RiverSource Trust Income Fund I*

372,834

RiverSource Trust Bond Index Fund II*

310,870

Evergreen Small Cap Value Fund

178,134

Brown Capital Management Small Company Fund

34,326

Self-Managed Brokerage Accounts

12,756

PIMCO Total Return Fund

(330,310)

Dreyfus Premier Emerging Markets Fund

(718,768)

Net appreciation in fair value of investments

$64,838,281

 

* Represents party known to be a party-in-interest to the Plan.

 

Note 8.

Non-Participant Directed Investments

 

Information about the net assets and the significant components of the changes in net assets relating to the non-participant directed investments was as follows:

 

Dec. 31,

Net assets:

2006

 

2005

Alliant Energy Corporation Common Stock*

$817,826

 

$68,338,101

RiverSource Trust Money Market Fund I*

12,120

 

987,313

Contributions receivable

--

 

378,296

Investment income receivable

1,659

 

5,358

 

$831,605

 

$69,709,068

 

 

 

Changes in net assets:

2006

 

Employer contributions

$379,399

 

 

 

 

Investment activity:

 

 

    Net appreciation in fair value of investments

136,954

 

    Investment income

16,385

 

 

 

 

Plan amendment related to diversification (Note 1)

(69,410,201)

 

 

($68,877,463)

 

* Represents party known to be a party-in-interest to the Plan.

 

Note 9.

Related Party Transactions

 

Certain Plan investments are shares of mutual funds and common trust funds managed by an affiliate of the Trustee and shares of common stock of the Company. As of Dec. 31, 2006 and 2005, the Plan held 3,649,180 and 3,831,237 shares of Alliant Energy Corporation common stock with a cost basis of $90,603,322 and $94,376,693, respectively. In 2006 and 2005, the Plan recorded dividend income of $4,317,068 and $3,980,853, respectively, from investments in common stock of the Company. These transactions qualify as exempt party-in-interest transactions.

 

11

Note 10. Reconciliation to Form 5500

 

Distributions payable to participants are not included within net assets available for benefits in the accompanying financial statements, however, they are recorded as liabilities in the Plan’s Form 5500. For 2006, net assets available for benefits in the accompanying financial statements are at contract value, however, they are recorded at fair value in the Plan’s Form 5500. The following table reconciles net assets available for benefits per the financial statements to the Plan’s Form 5500 as filed by the Company:

 

2006

 

2005

Net assets available for benefits per financial statements

$587,660,633

 

$499,241,183

Adjustments:

 

 

 

Fair value to contract value for fully

 

 

 

benefit-responsive investment contracts

(435,698)

 

--

Benefits requested not yet paid

(227,307)

 

(59,982)

Amounts reported per Form 5500

$586,997,628

 

$499,181,201

 

The following table reconciles the net increase in net assets available for benefits per the financial statements to the Form 5500 as filed by the Company for 2006:

 

 

Net increase

Amounts reported per financial statements

$88,419,450

Adjustments:

 

Changes in adjustment from fair value to contract value

 

for fully benefit-responsive investment contracts

(435,698)

Changes in benefits requested not yet paid

(167,325)

Amounts reported per Form 5500

$87,816,427

 

12

ALLIANT ENERGY CORPORATION
 
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)
 
AS OF DECEMBER 31, 2006
 
Identify of issue, borrower, Description of investment including maturity date,   Current
lessor, or similar party rate of interest, collateral, par or maturity value Cost Value
Registered Investment Companies   Evergreen Small Cap Value Fund, 427,150 shares   $10,249,354   $10,499,350  
    American Funds Growth Fund of America, 2,716,565 shares    60,800,760   89,293,482  
    PIMCO Total Return Fund, 3,024,733 shares   32,141,695   31,396,730  
    Dodge & Cox Stock Fund, 367,953 shares   47,398,951   56,466,030  
    Brown Capital Management Small Company Fund, 24,241 shares   700,661   790,268  
    Dreyfus Premier Emerging Markets Fund, 1,006,811 shares   22,305,242   21,233,653  
    American Funds EuroPacific Growth Fund, 913,251 shares   33,445,909   41,991,279  
    Buffalo Small Cap Fund, 977,795 shares   27,205,186   26,341,808  
   
Common/Collective Trusts   RiverSource Trust Money Market Fund I*, 6,619,693 shares   6,169,693   6,169,693  
    RiverSource Trust Equity Index Fund III*, 1,959,874 shares   59,752,962   78,104,900  
    RiverSource Trust Income Fund I*, 115,628 shares   7,998,593   8,292,283  
    RiverSource Trust Investment Grade Bond Fund*, 649,552 shares   10,362,833   11,435,370  
    RiverSource Trust Bond Index Fund II*, 582,261 shares   8,377,486   8,797,964  
    State Street Global Advisors S&P Midcap Index Fund, 348,109 shares   10,767,912   13,047,467  
   
Corporate Stocks: Common   Alliant Energy Corporation common stock*, 3,649,180 shares   90,603,322   137,820,283  
   
Corporate Bonds   BOAA-06-9, 6.00%, 2/25/37, par value $350,000   351,367   351,367  
    COUNTRYWIDE ALT TR 2006-HY12, 6.20%, 8/25/36, par value $206,546   207,933   208,694  
    CWALT 2006-22CB-CA, 6.00%, 5/25/36, par value $170,000   170,478   171,646  
    CWALT 2006-31CBA16, 6.00%, 11/25/36, par value $150,000   151,523   151,520  
    CWALT 06-43CB 1A4, 6.00%, 2/25/37, par value $175,000   176,613   175,978  
    BACM 2005-4-A1, 4.43%, 7/10/45, par value $119,940   119,942   117,949  
    BACM 2005-6-A2, 5.19%, 9/10/47, par value $175,000   175,882   174,694  
    BOAA 2003-1-A1, 5.00%, 2/25/33, par value $75,448   75,954   73,893  
    BOAMS 2004-E 2A6, 4.11%, 6/25/34, par value $150,000   148,781   147,083  
    BACM 2006-2-AAB, 5.72%, 5/10/36, par value $150,000   150,756   153,790  
    BSCMS 2005-PWR9-A1, 4.50%, 9/11/42, par value $186,923   187,390   183,856  
    BSCMS 2005-T20-A2, 5.13%, 10/12/42, par value $250,000   251,366   248,730  
    CDC COMMERCIAL MTGE, 5.68%, 11/15/30, par value $375,000   379,419   381,687  
    CD 2006-CD2-AAB, 5.57%, 1/15/46, par value $200,000   198,008   201,272  
    CPS 2006-A-A3, 5.10%, 10/15/10, par value $175,000   174,983   174,945  
    CWALT 2005-6CB-1A1, 7.50%, 4/25/35, par value $48,925   52,189   50,705  
    CWL 2005-10-AF6, 4.91%, 12/25/35, par value $20,000   19,999   19,485  
    CWL 2005-17-1AF2, 5.36%, 12/25/35, par value $125,000   124,998   124,297  
    CWALT INC 2005-54CB, 5.50%, 11/25/35, par value $59,139   60,100   59,161  
    CWALT INC 2005-43, 5.50%, 11/25/35, par value $63,223   64,132   63,247  
    CWALT 2005-64CB-1A, 5.50%, 12/25/35, par value $125,875   127,079   126,198  
    CWALT 2005-85CB-2A, 5.50%, 2/25/36, par value $151,775   151,645   151,710  
    CWALT 2006-SCB, 6.00%, 1/25/36, par value $262,564   263,610   262,547  
    CWHL 2006-HYB1-1A1, 5.39%, 3/20/36, par value $146,058   146,058   145,205  
    CWHL 2006-HYB5-2A2, 5.95%, 9/20/36, par value $276,426   276,232   278,143  
    CGCMT 2005-C3-A1, 4.39%, 5/15/43, par value $243,244   243,848   238,872  
    ARMT 2005-12-2A1, 5.71%, 3/25/36, par value $159,116   160,104   159,611  
    CSFB 2003-CPN1-A2, 4.60%, 3/15/35, par value $350,000   335,549   337,442  
    CSMC 2006-C4-A3, 5.47%, 9/15/39, par value $260,000   261,300   261,608  
    CSFB 2005-C4-A1, 4.77%, 8/15/38, par value $180,464   180,916   178,537  
    ARMT_06-1-2A1, 5.97%, 6/25/36, par value $210,203   211,615   210,241  
    CSMC 2006-C1-A2, 5.44%, 2/15/39, par value $175,000   175,875   176,406  
    CSFB-05-12-SA1, 7.00%, 12/25/35, par value $108,161   112,133   110,444  

13

ALLIANT ENERGY CORPORATION
 
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)
 
AS OF DECEMBER 31, 2006 (Continued)
 
Identify of issue, borrower, Description of investment including maturity date,   Current
lessor, or similar party rate of interest, collateral, par or maturity value Cost Value
Corporate Bonds (continued)   FRNK 2004-2-A4, 3.93%, 8/15/12, par value $175,000   $173,496   $172,608  
    GMACM 2004-HE2-A4, 3.65%, 10/25/33, par value $120,000  115,539   115,660  
    GECMC 2005-C3-A2, 4.85%, 7/10/45, par value $350,000  351,746   345,868  
    GCCFC 2003-C2 A3, 4.53%, 7/05/10, par value $325,000  314,366   316,591  
    GCCFC 2005-GG5-A1, 4.79%, 4/10/37, par value $213,267  213,267   211,418  
    HVMLT 2005-12-2A1A, 6.83%, 10/19/35, par value $115,381  117,977   118,813  
    HERTZ VEHICLE FINANCING, 4.93%, 2/15/10, par value $150,000  149,991   149,661  
    INDX 2005-AR25-A1, 5.88%, 12/25/35, par value $84,536  85,398   84,665  
    INDX 2006-AR13-1A1, 6.10%, 7/25/36, par value $184,141  185,666   184,592  
    INDYMAC LN TR 2006-AR1, 5.96%, 8/25/36, par value $405,330  406,882   407,602  
    JPMCC 2003-LN1-A1, 4.13%, 10/15/37, par value $93,582  89,762   90,472  
    JPMCC 2003-C1-A1, 4.27%, 1/12/37, par value $172,042  170,275   167,723  
    JPMCC 2005-CIBC12, 4.85%, 9/12/37, par value $175,000  167,316   170,996  
    JPMCC 2006-CB16, 5.55%, 5/12/45, par value $275,000  276,367   278,949  
    LBUBS 2005-C1-A1, 4.06%, 2/15/30, par value $72,355  72,715   70,981  
    LBART 2005-B-A3, 4.41%, 5/15/10, par value $200,000  200,000   198,552  
    MALT 2004-13 7A1, 6.50%, 11/25/34, par value $277,445  278,572   278,633  
    MLMT 2005-CIP1-A1, 4.63%, 5/12/10, par value $179,681  179,681   177,280  
    MLMT 2005-CK1-A1, 5.03%, 11/12/37, par value $157,375  157,765   156,766  
    MSC 2003-T11 A2, 4.34%, 6/13/41, par value $250,000  243,213   244,372  
    MSM 2004-2AR 3A, 5.05%, 2/25/34, par value $121,739  124,668   120,164  
    MSC 2006-HQ9-AAB, 5.68%, 7/20/44, par value $200,000  201,091   204,159  
    POPLR 2005-5-AF3, 5.09%, 11/25/35, par value $175,000  174,999   173,223  
    RAMC 2006-2-AF3, 5.69%, 8/25/36, par value $135,000  135,000   135,612  
    RAMC 2005-3-AF3, 4.77%, 10/25/35, par value $125,000  124,553   123,457  
    RAMC 2005-4-A3, 5.56%, 2/25/36, par value $70,000  70,000   69,736  
    RAMC 2006-1-AF3, 5.61%, 5/25/36, par value $235,000  234,994   234,816  
    RALI SER 2003-QS4 ABS, 5.50%, 9/25/33, par value $18,719  19,244   18,667  
    RASC 2004-KS8 AI3, 3.84%, 9/25/34, par value $82,113  82,099   81,099  
    RALI 2006-QS3-1A10, 6.00%, 3/25/36, par value $107,369  108,090   108,610  
    SQALT 2006-1-A2, 6.12%, 2/25/36, par value $94,991  95,696   96,245  
    SARM 2005-15-4A1, 5.52%, 7/25/35, par value $182,280  183,954   180,628  
    SARM-06-5:4A1 CMO FLOAT% 7/25/36, 5.97%, 6/25/36, par value $139,091  138,222   139,477  
    WAMU MTG PASS-THROUGH CTFS 2005, 5.30%, 12/25/35, par value $113,963  112,476   113,042  
    WBCMT 2003-C8-A2, 3.89%, 11/15/35, par value $150,000  150,745   146,124  
    WBCMT 2005-C18-A2, 4.66%, 4/15/42, par value $175,000  170,912   171,664  
    WBCMT 2005-C18-A4, 4.93%, 4/15/42, par value $200,000  191,758   194,653  
    WBCMT 2005-C19-A1, 4.17%, 6/15/42, par value $136,888  136,884   134,101  
    WFMBS 2005-5-3PT3, 5.50%, 5/25/35, par value $267,702  267,080   263,017  
    WFMBS 2006-AR6-2A2, 5.08%, 4/25/36, par value $185,430  182,569   183,042  
    WELLS FARGO MTG BACKED SECS 2006, 5.11%, 3/25/36, par value $142,342  140,190   140,682  
    CS FIRST BOSTON MTGE SECURITIES, 5.10%, 8/15/38, par value $250,000  249,793   248,483  
    WFMBS, 5.00%, 10/25/35, par value $315,472  305,845   303,346  

14

ALLIANT ENERGY CORPORATION
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)
 
AS OF DECEMBER 31, 2006 (Continued)
 
Identify of issue, borrower, Description of investment including maturity date,   Current
lessor, or similar party rate of interest, collateral, par or maturity value Cost Value
Government and Agency Obligations   FNMA 30YR TBA, 5.00%, 1/01/35, par value $400,000   $391,672   $386,125  
    FNMA 15YR TBA, 5.50%, 1/01/15, par value $350,000   351,531   349,891  
    FNMA TBA, 5.50%, 1/01/31, par value $1,000,000   995,906   988,125  
    FNMA 30YR TBA, 6.00%, 9/01/28, par value $375,000   379,250   377,460  
    FNMA 30YR TBA, 6.50%, 1/01/30, par value $375,000   382,676   382,031  
    FGLMC GOLD 30 YR TBA, 5.50%, 1/01/37, par value $375,000   373,403   370,781  
    FHLMC TBA, 6.00%, 1/01/33, par value $1,100,000   1,113,063   1,107,909  
    FHLMC GOLD #E91326, 6.50%, 9/01/17, par value $58,791   62,282   60,149  
    FHLMC GOLD #E97247, 5.00%, 6/01/18, par value $90,446   92,368   89,141  
    FGOLD 10 YR #G12100, 5.00%, 11/01/13, par value $73,448  71,979   72,603  
    FHLMC #1G1067, 5.70%, 7/01/36, par value $244,966   243,942   246,086  
    FHLMC (NON GOLD) ARM #1G2450, 5.93%, 8/01/36, par value $319,236   321,518   322,697  
    FHLMC #1G2496 ARM, 6.21%, 9/01/36, par value $123,094   124,830   124,164  
    FHLMC GOLD #C66932, 6.00%, 5/01/32, par value $49,000   49,107   49,478  
    FED HOME LN BANK, 4.63%, 1/18/08, par value $30,000   29,964   29,834  
    FHLB, 5.25%, 2/13/08, par value $25,000   24,989   25,013  
    FHLMC REF NOTE, 5.13%, 10/15/08, par value $85,000   87,547   85,109  
    FHLMC, 3.88%, 6/15/08, par value $45,000   43,616   44,234  
    FNMA BENCHMARK, 4.50%, 10/15/08, par value $85,000   84,867   84,242  
    FNMA 15YR #252260, 6.00%, 3/01/10, par value $278,053   276,706   282,396  
    FNMA #254187, 5.00%, 12/01/08, par value $156,138   155,284   155,481  
    FNMA #254291, 7.00%, 4/01/17, par value $67,501   71,994   69,388  
    FNMA #254757, 5.00%, 3/31/13, par value $78,031   81,542   77,015  
    FNMA #254793, 5.00%, 7/01/33, par value $121,710   119,922   117,734  
    FNMA #357324, 5.00%, 1/01/33, par value $293,246   282,341   283,763  
    FNMA #387608, 4.80%, 9/01/15, par value $220,384   212,008   214,963  
    FNMA #462236, 5.44%, 7/01/16, par value $124,606   127,366   125,884  
    FNMA #462237, 5.52%, 7/01/16, par value $149,550  153,703   151,904  
    FNMA #535170, 5.50%, 9/01/14, par value $79,436   81,968   79,775  
    FNMA #545701, 7.00%, 7/01/12, par value $41,789   44,662   42,014  
    FNMA #545864, 5.50%, 8/01/17, par value $140,757   142,835   141,245  
    FNMA #555528, 6.00%, 4/01/33, par value $264,204   266,475   266,615  
    FNMA #555591, 5.50%, 7/01/33, par value $477,795   476,077   472,924  
    FNMA #555740, 4.50%, 9/01/18, par value $185,143   181,383   178,982  
    FNMA #640996, 7.50%, 5/01/32, par value $49,161   52,602   51,100  
    FNMA #646147, 7.00%, 6/01/32, par value $144,573   151,485   149,517  
    FNMA #648349, 6.00%, 6/01/17, par value $55,320   57,862   56,246  
    FNMA #677377, 5.50%, 1/01/33, par value $313,055   309,925   309,928  
    FHLMC 2492-B, 5.50%, 5/15/13, par value $266,406  278,103   265,977  
    FNMA #200394, 5.50%, 7/25/23, par value $167,804   175,172   167,171  
    FHLMC 2617 HD, 7.00%, 6/15/16, par value $78,099   84,835   80,469  
    FNMA 2003-133 GB, 8.00%, 12/25/26, par value $39,873   43,692   42,020  
    FHLMC 2641, 6.50%, 1/15/18, par value $82,000   87,503   84,158  
    FNMA 2004-W3 A15, 5.00%, 5/25/34, par value $85,745   89,725   85,087  
    FNMA 2004-60 PA, 5.50%, 4/25/34, par value $119,532  123,482   119,457  

15

ALLIANT ENERGY CORPORATION
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)
 
AS OF DECEMBER 31, 2006 (Continued)
 
Identify of issue, borrower, Description of investment including maturity date,   Current
lessor, or similar party rate of interest, collateral, par or maturity value Cost Value
Government and Agency Obligations   FHLMC 2657 NT, 5.00%, 1/15/16, par value $89.245   $92,885   $88,780  
     (continued)   FHLMC 2672 NT, 5.00%, 2/15/16, par value $115,702   120,497   115,059  
    FHLMC 2662 DB, 5.00%, 2/15/16, par value $84,800  88,219   84,349  
    FHLMC 2750 DB, 4.50%, 5/15/15, par value $114,720  117,462   113,447  
    FHLMC 2843-BA, 5.00%, 1/15/18, par value $89,383  91,593   88,426  
    FHLMC 2907-AG, 4.50%, 3/15/19, par value $89,629  89,601   87,325  
    FNMA #685433, 6.50%, 3/01/33, par value $90,026  95,069   92,222  
    FNMA #704265, 5.50%, 5/01/33, par value $343,226  336,402   339,728  
    FNMA #705304, 4.92%, 6/01/33, par value $133,277  135,224   130,763  
    FEDERAL NATL MTG ASSN GTD MTG, 6.00%, 12/01/33, par value $463,189  462,320   467,094  
    FNMA #725090, 4.82%, 11/01/33, par value $118,058  117,431   114,400  
    FNMA #725425, 5.50%, 4/01/34, par value $543,860  532,572   538,352  
    FNMA ARM #725737, 4.53%, 8/01/34, par value $82,172  81,183   81,649  
    FNMA #725773, 5.50%, 9/01/34, par value $321,984  312,073   318,532  
    FNMA #725815, 6.00%, 12/01/33, par value $158,691  160,105   160,029  
    FNMA #728599, 5.00%, 7/01/33, par value $702,427  686,732   679,478  
    FNMA #735057, 4.50%, 1/01/19, par value $159,929  153,782   154,659  
    FNMA #735935, 5.00%, 12/01/18, par value $291,055  286,189   287,036  
    FNMA #741897, 5.00%, 10/01/33, par value $91,338  88,198   88,353  
    FNMA #745563, 5.50%, 8/01/34, par value $482,830  472,173   477,908  
    FNMA #745727, 5.26%, 5/01/16, par value $248,751  246,779   248,306  
    FNMA #745802, 6.00%, 7/01/36, par value $364,011  365,831   366,475  
    FNMA #763798, 5.50%, 3/01/34, par value $244,133  247,185   241,729  
    FNMA #764082, 4.78%, 1/01/34, par value $88,180  89,627   86,969  
    FNMA ARM #799769, 5.05%, 11/01/34, par value $100,630  102,642   99,931  
    FNMA ARM #801344, 5.07%, 10/01/34, par value $104,480  106,374   104,404  
    FNMA #809534, 5.09%, 2/01/35, par value $87,822  88,999   87,574  
    FNMA ARM #826908, 5.12%, 8/01/35, par value $163,863  163,453   161,464  
    FNMA #844705, 5.76%, 12/01/35, par value $129,135  130,386   129,336  
    FNMA ARM #845070, 5.09%, 12/01/35, par value $180,261  180,359   179,331  
    FNMA ARM #849082, 5.84%, 1/01/36, par value $87,807  88,888   88,342  
    FNMA ARM #866097, 6.17%, 2/01/36, par value $166,596  169,043   169,513  
    FNMA ARM #872753, 5.92%, 6/01/36, par value $95,854  96,348   96,442  
    FNMA #878661, 5.50%, 2/01/36, par value $456,684  438,417   449,322  
    FNMA #881629, 5.50%, 2/01/36, par value $442,416  424,927   435,284  
    FNMA #883267, 6.50%, 7/01/36, par value $171,092  173,818   175,494  
    FNMA ARM #886461, 6.19%, 8/01/36, par value $93,297  94,128   94,483  
    FNMA #886762, 7.00%, 9/01/36, par value $337,625  347,701   348,097  
    FNMA ARM #887096, 5.81%, 7/01/36, par value $215,066  215,663   217,716  
    FNMA ARM #900197, 5.97%, 10/01/36, par value $124,972  126,364   125,751  
    GNMA II #003501, 6.00%, 1/20/34, par value $452,770  446,544   458,222  
    GNMA II #003920, 6.00%, 11/20/36, par value $249,611  253,511   252,467  
    UST INFLATION INDEX, 3.38%, 1/15/07, par value $1,200,000  1,535,837   1,524,919  
    U.S. TREASURY NOTE, 2.25%, 2/15/07, par value $620,000  609,934   617,917  
    U.S. T-BOND, 3.38%, 2/15/08, par value $70,000  68,179   68,778  
    U.S. TREASURY NOTE, 4.25%, 11/30/07, par value $140,000  139,042   139,037  
    UST NOTE/BOND, 4.88%, 5/31/08, par value $40,000  39,903   39,981  
    U.S. TREASURY NOTE, 4.88%, 10/31/08, par value $530,000  532,010   530,248  
    U.S. TREASURY NOTE, 4.63%, 10/31/11, par value $40,000  40,241   39,855  
    U.S. TREASURY NOTE, 4.63%, 11/15/16, par value $440,000  444,594   437,113  
    U.S. TREASURY NOTE, 4.50%, 11/30/11, par value $140,000  140,875   138,753  
    FNMA 2004-W10 A23, 5.00%, 8/25/34, par value $125,000  128,770   124,109  

16

ALLIANT ENERGY CORPORATION
 
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)
 
AS OF DECEMBER 31, 2006 (Continued)
 
Identify of issue, borrower, Description of investment including maturity date,   Current
lessor, or similar party rate of interest, collateral, par or maturity value Cost Value
Investment Contracts   Monumental Life Insurance Company, 5.24%, 12/31/50          
        Synthetic Guaranteed Investment Contract Wrapper                    $-                     $-  
    Bank of America NA, 5.39%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -    24,503  
    Rabobank International, 5.29%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    - 23,585  
    IXIS Capital Markets, 4.98%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -     42,115  
    JP Morgan Chase & Co., 5.17%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -     14,044  
    UBS Warburg, 5.28%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -     26,379  
    State Street Bank and Trust Company, 5.03%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -     27,671  
    AIG Financial Products Corp., 4.72%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    -     30,530  
    JP Morgan Chase II, 5.10%, 12/31/50 
        Synthetic Guaranteed Investment Contract Wrapper                    - -  
Participant-Directed Brokerage Accounts   Self-Managed Brokerage Accounts          359,209 381,185  
Participant Promissory Notes*   Maximum allowable loan -- $50,000          
    Various interest rates -- 5.0% to 10.5% 
    Primarily maturing within 5 years                    -          9,305,638  
 
          $464,227,645 $587,004,658  
 

* Represents party known to be a party-in-interest to the Alliant Energy Corporation 401(k) Savings Plan.

17

ALLIANT ENERGY CORPORATION
 
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV, LINE 4i - SCHEDULE OF ASSETS (ACQUIRED AND DISPOSED OF WITHIN YEAR)
 
FOR THE YEAR ENDED DECEMBER 31, 2006
 
  Description of investment    
Identity including maturity date,    
of issue, borrower, lessor, rate of interest, collateral, Cost of Proceeds of
or similar party par or maturity value Acquisitions Dispositions
Corporate Bonds   ARMT 2006 - 2 - CB1, 6.24%, 5/25/36   $125,541   $126,641  
    COUNTRYWIDE ALT TR, 6.20%, 8/25/36  18,578   18,454  
    CWALT 2005 - 64CB - 1A, 5.50%, 12/25/35  19,137   18,956  
    CWALT 2005 - 85CB - 2A, 5.50%, 2/25/36  20,431   20,449  
    CWALT 2006 - 2CB, 6.00%, 1/25/36  37,585   37,436  
    CWHL 2006 - HYB1 - 1A1, 5.39%, 3/20/36  28,942   28,942  
    CWHL 2006 - HYB5 - 2A2, 5.95%, 9/20/36  22,575   22,591  
    CCCIT 06 - B2 - B2, 5.15%, 3/07/11  399,716   393,891  
    ARMT 2005 - 12 - 2A1, 5.71%, 3/25/36  36,503   36,278  
    ARMT_06 - 1 - 2A1, 5.97%, 6/25/36  40,065   39,797  
    INDX 2006 - AR13 - 1A1, 6.10%, 7/25/36  15,990   15,859  
    INDYMAC LN TR 2006, 5.96%, 8/25/36  19,745   19,670  
    JPMCC 2003 - LN1 - A1, 4.13%, 10/15/37  15,011   15,649  
    MALT 2004 - 13 7A1, 6.50%, 11/25/34  55,230   55,007  
    MLMT 2006 - C1 - A4, 5.84%, 5/12/39  224,536   229,474  
    RALI 2006 - QS3 - 1A10, 6.00%, 3/25/36  11,303   11,228  
    SQALT 2006 - 1 - A2, 6.12%, 2/25/36  26,819   26,622  
    SARM_06 - 5 - 4A1 CMO, 5.97%, 6/25/36  10,841   10,909  
    TBW 2006 - 2 - 6A1, 7.00%, 7/25/36  152,748   152,011  
    WAMU MTG PASS-THRO, 5.30%, 12/25/35  3,477   3,523  
    WBCMT 2006 - C25 - APB, 5.95%, 5/15/43  200,988   203,773  
    WFMBS 2006 - AR6 - 2A2, 5.08%, 4/25/36  14,345   14,570  
    WELLS FARGO MTG BA, 5.11%, 3/25/36  2,119   2,152  

18

ALLIANT ENERGY CORPORATION
401(k) SAVINGS PLAN
 
FORM 5500, SCHEDULE H, PART IV
 
LINE 4j - SCHEDULE OF REPORTABLE TRANSACTIONS
 
FOR THE YEAR ENDED DECEMBER 31, 2006
 
Identity Total Total Total Net Adjusted Net
of Party Involved and Number of Value of Number Selling Cost of Gain
Description of Assets Purchases Purchases (1) of Sales Price (1) Assets Sold (Loss)
Single Transaction Exceeds 5% of Value:                
 
None.
Series of Transactions With Same Broker Exceeds 5% of Value:
 
None.
Series of Transactions In Same Security Exceeds 5% of Value:
 
RiverSource Trust Money Market Fund I*  466   $72,644,810   449   $73,339,694   $73,339,694   $- 
Single Transaction With One Broker Exceeds 5% of Value:
 
None.

     (1) The purchase/selling price was equal to the fair value on the date of purchase/sale.
    * Represents party known to be a party-in-interest to the Alliant Energy 401(k) Savings Plan.

19  

SIGNATURES

 

Pursuant to the requirements of the Securities Exchange Act of 1934, the Total Compensation Committee, which administers the Plan, has duly caused this Annual Report to be signed on its behalf by the undersigned, thereunto duly authorized, on this 28th day of June 2007.

 

 

 

ALLIANT ENERGY CORPORATION

 

401(k) SAVINGS PLAN

 

 

 

 

  /s/ Christopher J. Lindell

 

Christopher J. Lindell

 

 

 

The foregoing person is the Vice President - Shared Services

 

of Alliant Energy Corporation and Alliant Energy Corporate

 

Services, Inc., and the Chairperson of the Alliant Energy

 

Corporation Total Compensation Committee.

 

 

 

 

 

 

 

20

EXHIBIT INDEX TO ANNUAL REPORT ON FORM 11-K

 

 

ALLIANT ENERGY CORPORATION

401(k) SAVINGS PLAN

 

FOR THE YEAR ENDED DECEMBER 31, 2006

 

 

 

 

 

Page Number in

 

 

Sequentially Numbered

Exhibit No.

Exhibit

Form 11-K

23

Consent of Independent Registered Public Accounting Firm

22

 

 

21