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  As Of               Filer                 Filing     As/For/On Docs:Pgs              Issuer               Agent

 4/07/06  NML Variable Annuity Acct C o..Co N-8A        4/07/06    1:1203                                   RR Donnelley/FA

Document/Exhibit                   Description                      Pages   Size 

 1: N-8A        Nml Variable Annuity Account C                      HTML  7,417K 

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-8A

NOTIFICATION OF REGISTRATION FILED PURSUANT TO

SECTION 8(a) OF THE INVESTMENT COMPANY ACT OF 1940

The undersigned investment company hereby notifies the Securities and Exchange Commission that it registers under and pursuant to the provisions of Section 8(a) of the Investment Company Act of 1940 and in connection with such notification of registration submits the following information:

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TRUSTEES – As of April 1, 2006

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EXECUTIVE OFFICERS – As of April 1, 2006

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OTHER OFFICERS – As of December 1, 2005

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The business addresses for all of the executive officers and other officers is 720 East Wisconsin Avenue, Milwaukee, Wisconsin 53202.

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SIGNATURES

Pursuant to the requirements of the Investment Company Act of 1940, the sponsor of the registrant has caused this notification of registration to be signed on behalf of the registrant in the City of Milwaukee, and State of Wisconsin, on the 7th day of April, 2006.

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December 31, 2005              THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY

Group Combination Annuity Account C

Letter to Contract Owners

December 31, 2005

In a year marked by contrasts, the economy and the markets held up remarkably well throughout 2005. The destructive hurricanes that hit the Southern coast threatened to derail economic growth mid-year but, surprisingly, the economy never skipped a beat. On the contrary, the potential for rebuilding turned what was considered a disaster into a potential economic stimulus that bolstered stock market returns late in the year, particularly in the Industrials and Materials sectors. Substantially higher energy prices affected the entire country but failed to dampen consumer spending, and consumer confidence ended the year higher.

Buoyed by fiscal and monetary policies aimed at constraining taxes and raising interest rates gradually, U.S. gross domestic product increased at a healthy rate in 2005. Promised government spending in the wake of Hurricane Katrina, coupled with rising home values throughout most of the year, aided the economy and boosted consumer confidence. Housing continued to play a major role in economic activity during 2005, as rising home values allowed homeowners to borrow against the equity in their homes at attractive long-term rates. Huge mortgage equity withdrawals fueled consumer demand for everything from home appliances to autos.

The U.S. stock market advanced overall for the third consecutive year in 2005, though returns were lower than in the previous two years. Despite rising oil prices, higher short-term interest rates and the hurricanes, U.S. corporations enjoyed a solid year, reporting good corporate earnings and strong consumer demand. The market enjoyed low volatility throughout the year, and all major indexes posted gains. The S&P 500 Index — a benchmark of U.S. equity performance — gained 4.91% for the year, while mid- capitalization stocks and international equities were the clear winners in 2005. Mid-cap stocks gained 12.56%, as measured by the S&P MidCap 400 Index, and foreign stocks gained 14.02%, as measured by the EAFE Index. Energy was once again the top performing sector for the year.

It was a fairly uneventful year in the bond market, which was also marked by low volatility. Bonds posted a positive, but small, gain of 2.57% for the year, as measured by the Citigroup US Broad Investment Grade Bond Index. High yield bonds, which had enjoyed above-average returns in 2003 and 2004, gained 2.07% for the year, as measured by the Citigroup High Yield Cash Pay Index. The yield on the 10-year Treasury bond barely moved over the twelve-month period, ending the year at 4.39%, up from 4.21% on January 1, 2005. Short-term interest rates, however, continued to climb as the Federal Reserve Board raised rates eight times in 2005, increasing the federal funds rate by 200 basis points, or 2%, to 4.25% at year end, the highest the rate has been since May 2001.

While the consensus calls for 3.5% GDP growth in the first half of 2006, we believe several factors may work together to keep growth lower in the coming months. Gasoline prices were high throughout 2005, but higher home heating costs only began to reach consumers late in the year. Taken together, higher energy costs may put a dampening effect on other consumer spending as we head into the new year. We expect positive, but slower, growth in 2006, given a continued slowdown in housing sales, a fairly valued stock market, and additional interest rate hikes that could be reflected in higher mortgage rates. We caution investors to recognize that risks exist this late in the business cycle, when slower economic growth is typical.

Despite our tempered enthusiasm, the remarkable resiliency of the U.S. economy cannot be understated. Consumer confidence remains high despite concerns, and productivity continues to be a real positive for our economy. In the past, U.S. corporations have continued to find ways to compete successfully in the global marketplace, and we see no fundamental reason for this to change.

Our best advice continues to be to keep your expectations in line. Slow, steady growth is best achieved with a well-thought-out plan and a well-balanced portfolio of investments. Working with your financial representative to determine the mix of assets best suited to your risk level and stage of life is the key to long-term investment success.

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How To Get More Information

Northwestern Mutual Express:

1-800-519-4665

Contact Your Northwestern Mutual Investment Services representative, if you have questions about your contract or any of the contract owner privileges.

Information on the Internet:

Northwestern Mutual Financial Network

WWW.NMFN.COM

For information about Northwestern Mutual visit us on our Website.

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Contents

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Performance Summary    as of December 31, 2005

Front Load Contract

All total return figures are for divisions of NML Variable Annuity Account C and are based on the change in unit value, which reflects expenses, such as account charges and fees applied at the contract level; figures for the Front Load contract reflect a maximum sales load of 4.5%; figures for the Simplified Load contract reflect an installation fee in the amount of $750. The data reflects an initial contract value of $25,000, the minimum size.

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Performance Summary, continued    as of December 31, 2005

Front Load Contract

All total return figures are for divisions of NML Variable Annuity Account C and are based on the change in unit value, which reflects expenses, such as account charges and fees applied at the contract level; figures for the Front Load contract reflect a maximum sales load of 4.5%; figures for the Simplified Load contract reflect an installation fee in the amount of $750. The data reflects an initial contract value of $25,000, the minimum size.

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Annual Report December 31, 2005

Northwestern Mutual Series Fund, Inc.

A Series Fund Offering Eighteen Portfolios

Northwestern Mutual Series Fund, Inc.

 Table of Contents

The views expressed in the portfolio manager commentaries set forth in the following pages reflect those of the portfolio managers only through the end of the period covered by this report and do not necessarily represent the views of any affiliated organization. These views are subject to change at any time based upon market conditions or other events and should not be relied upon as investment advice. Mason Street Advisors, LLC. disclaims any responsibility to update these views.

   Small Cap Growth Stock Portfolio

The Small Cap Growth Stock Portfolio seeks long-term growth of capital. The Portfolio seeks to achieve this objective by investing in emerging companies with rapidly growing revenues and earnings supported by financial strength and capable management. Holdings are smaller companies with a median market capitalization of approximately $1 billion; the range of market capitalization is generally between $200 million and $3 billion. The manager of this Portfolio has a strong orientation to quality and a commitment to broad diversification. In evaluating individual companies, factors such as the growth rates of revenues and earnings, opportunities for margin expansion, financial strength and quality of management are important variables.

The overall U.S. stock market advanced for the third consecutive year in 2005, though returns were lower than in the previous two years. Despite rising oil prices, higher short-term interest rates, and two devastating Gulf Coast hurricanes, stocks rallied thanks to solid economic growth, brisk merger activity, and better-than-expected corporate earnings. Small- and mid-capitalization stocks outperformed large-cap stocks once again this year; however, mid-cap stocks took the lead in 2005 over both large- and small-cap issues.

For the year ended December 31, 2005, the Small Cap Growth Portfolio returned 11.18%, substantially outperforming both the Russell 2000 Index, which had a return of 4.55%, and the S&P SmallCap 600 Index, which returned 7.68% for the same period. (These indices are unmanaged, cannot be invested in directly, and do not include administrative expenses or sales charges.) The Portfolio also outperformed its peer group, Small-Cap Growth Funds, which had an average return of 7.50% for the same period, according to Lipper Analytical Services, Inc. (“Lipper”), an independent mutual fund ranking agency.

The Portfolio’s outperformance for 2005 can be attributed primarily to good stock selection, particularly in the Consumer Discretionary, Health Care and Energy sectors. Stocks of special note include Health Care holdings Radiation Therapy Services, Inc. and LCA Vision, Inc., Technology holding Plexus Corp. and Greenhill & Co. Inc., an investment banking firm. Each of these stocks reported strong growth rates during the year. Our Energy holdings also added to performance, as most stocks in the sector experienced exceptional gains in 2005 due to the rising prices of oil and natural gas and the continued strong demand for energy worldwide. One Energy stock that added substantially to our return in 2005, Grant Prideco, Inc., is also among the Portfolio’s top ten holdings. The company, which supplies steel tubing for the Energy sector, benefited from increased demand in oil but also gained synergies from a recent acquisition.

Several stocks in the Portfolio turned in disappointing returns for 2005, including Kanbay International, an Indian IT outsourcing company which experienced a slowdown in business, and Westell Technologies, Inc., a telecom equipment company that was hurt as one of its major customers scaled back orders. Cogent Inc., a fingerprint technology company that lagged in 2005 as business contracts slowed, and Tekelec, a Technology holding that experienced a slow down in customer demand, also detracted from performance.

Sector weightings had a slightly negative impact on total return for 2005. We were overweight Telecom Services, which hurt performance as that sector had negative performance for the year. In contrast, our underweight position in Industrials negatively impacted return because that sector experienced above-average gains during 2005.

Heading into 2006, we believe the Portfolio is well positioned to take advantage of what we expect to be a pullback in the more aggressive sectors of the market. The Portfolio does not hold large positions in those areas, so a correction would actually benefit us. Throughout the year, we intend to remain focused on individual stock selection, looking for companies with above-average growth potential, and we believe we should continue to find attractive candidates for the Portfolio.

Small Cap Growth Stock Portfolio

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Small Cap Growth Stock Portfolio

This chart assumes an initial investment of $10,000 made on 4/30/99 (commencement of the Portfolio’s operations). Returns shown reflect fee waivers, deductions for management and other portfolio expenses, and reinvestment of all dividends. In the absence of fee waivers, total return would be reduced. Returns exclude deductions for separate account sales loads and account fees. Total returns, which reflect deduction of charges for the separate account, are shown beginning on page iv of the Performance Summary of the Separate Account report.

Stocks of smaller or newer companies, such as those held in this Fund, are more likely to realize more substantial growth as well as suffer more significant losses than larger or more established issuers. Investments in such companies can be both more volatile and more speculative. Investing in small company stocks involves a greater degree of risk than investing in medium or large company stocks.

Since the Portfolio invests primarily in small capitalization issues, the indices that best reflect the portfolio’s performance are the Standard and Poor’s (S&P) SmallCap 600 Index and Russell 2000 Index. The indices cannot be invested in directly and do not include sales charges.

The Russell 2000 Index measures the performance of the 2,000 smallest companies in the Russell 3000 Index. The Russell 3000 Index measures the performance of the 3,000 largest U.S. companies based on total market capitalization. These 3,000 companies represent approximately 98% of the investable US equity market. As of the latest reconstitution, the average market capitalization of companies in the Russell 3000 was approximately $4.8 billion; the median market capitalization was approximately $944.7 million. Market capitalization of companies in the Index ranged from $386.9 billion to $182.6 million.

The Russell 2000 Index represents approximately 8% of the total market capitalization of the Russell 3000 Index. As of the latest reconstitution, the average market capitalization of companies in the Russell 2000 was approximately $664.9 million; the median market capitalization was approximately $539.5 million. The largest company in the Index had an approximate market capitalization of $1.8 billion.

The Standard & Poor’s SmallCap 600 Index is an unmanaged index of 600 selected common stocks of smaller U.S. -based companies compiled by Standard & Poor’s Corporation. As of December 31, 2005, the 600 companies in the composite had a median market capitalization of $793.1 million and total market value of $564.3 billion. The SmallCap 600 represents approximately 2.9% of the market value of Compustat’s database of over 9,443 equities.

The Lipper Variable Insurance Products (VIP) Small Cap Growth Funds Average is calculated by Lipper Analytical Services, Inc. and reflects the average investment return of portfolios underlying variable life and annuity products. The category consists of Funds that, by portfolio practice, invest at least 75% of their equity assets in companies with market capitalizations (on a three-year weighted basis) less than 250% of the dollar-weighted median of the smallest 500 of the middle 1,000 securities of the S&P SuperComposite 1500 Index. Small-cap growth funds typically have an above-average price-to-earnings ratio, price-to-book ratio, and three-year sales-per-share growth value, compared to the S&P SmallCap 600 Index. Source: Lipper, Inc.

Sector Allocation is based on Net Assets.

Sector Allocation and Top 10 Holdings are subject to change.

Investing in small company stocks involves a greater degree of risk than investing in medium or large company stocks.

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Small Cap Growth Stock Portfolio

Small Cap Growth Stock Portfolio

Expense Example

As a shareholder of the Fund, you incur two types of costs: (1) transaction costs and (2) ongoing costs, including management fees and other Fund expenses. This Example is intended to help you understand your ongoing costs (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds.

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (July 1, 2005 to December 31, 2005).

Actual Expenses

The first line of the table below provides information about actual account values and actual expenses. You may use the information in this line, together with the amount you invested, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number in the first line under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes

The second line of the table below provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs or separate account charges. Therefore, the second line of the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs or separate account charges were included, your costs would have been higher.

Small Cap Growth Stock Portfolio

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Small Cap Growth Stock Portfolio

Northwestern Mutual Series Fund, Inc.

Schedule of Investments

December 31, 2005