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Filed Pursuant to Rule 497
Registration Statement Nos. 333-180689 and 333-180690

This preliminary prospectus supplement relates to an effective registration statement under the Securities Act of 1933, as amended, but the information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell and are not soliciting an offer to buy these securities in any jurisdiction where the offer and sale is not permitted.

Subject to Completion, Dated December 3, 2012

PRELIMINARY PROSPECTUS SUPPLEMENT

(to Prospectus dated July 10, 2012)

3,000,000 Shares

New Mountain Finance Corporation

Common Stock

New Mountain Finance Corporation (“NMFC”) is a holding company with no direct operations of its own, and its only business and sole asset is its ownership of common membership units of New Mountain Finance Holdings, L.L.C. (the “Operating Company”). The Operating Company is an externally managed business development company managed by New Mountain Finance Advisers BDC, L.L.C. and is the operating company for NMFC’s business. NMFC and the Operating Company each have elected to be treated as a business development company under the Investment Company Act of 1940. The Operating Company’s investment objective is to generate current income and capital appreciation through the sourcing and origination of debt securities at all levels of the capital structure, including first and second lien debt, notes, bonds and mezzanine securities. Prior to this offering, NMFC owned approximately 56.1% of the common membership units of the Operating Company and New Mountain Finance AIV Holdings Corporation owned approximately 43.9% of the common membership units of the Operating Company.

We are offering for sale 3,000,000 shares of NMFC’s common stock. We have granted the underwriters a 30-day option to purchase up to 450,000 additional shares of NMFC’s common stock at the public offering price, less the underwriting discounts and commissions.

NMFC’s common stock is listed on the New York Stock Exchange under the symbol “NMFC”. On November 30, 2012, the last reported sales price on the New York Stock Exchange for NMFC’s common stock was $15.18 per share.

An investment in NMFC’s common stock is very risky and highly speculative. Shares of closed-end investment companies, including business development companies, frequently trade at a discount to their net asset value. In addition, the companies in which NMFC invests, through the Operating Company, are subject to special risks. See “Risk Factors” beginning on page 19 of the accompanying prospectus to read about factors you should consider, including the risk of leverage, before investing in NMFC’s common stock.

This prospectus supplement and the accompanying prospectus contain important information about NMFC and the Operating Company that a prospective investor should know before investing in NMFC’s common stock. Please read this prospectus supplement and the accompanying prospectus before investing and keep it for future reference. NMFC and the Operating Company file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission (http://www.sec.gov), which is available free of charge by contacting NMFC by mail at 787 Seventh Avenue, 48th Floor, New York, New York 10019 or on our website at http://www.newmountainfinance.com. Information contained on our website is not incorporated by reference into this prospectus supplement and the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement and the accompanying prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares against payment in New York, New York on or about        , 2012.

Joint-Lead Bookrunners

Co-Lead Managers

Prospectus Supplement dated                 , 2012.

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PROSPECTUS SUPPLEMENT

PROSPECTUS

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ABOUT THIS PROSPECTUS SUPPLEMENT

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus. Neither we nor the underwriters have authorized any other person to provide you with different information from that contained in this prospectus supplement or the accompanying prospectus. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer to buy, any shares of our common stock by any person in any jurisdiction where it is unlawful for that person to make such an offer or solicitation or to any person in any jurisdiction to whom it is unlawful to make such an offer or solicitation. The information contained in this prospectus supplement and the accompanying prospectus is complete and accurate only as of their respective dates, regardless of the time of their delivery or sale of our common stock. This prospectus supplement supersedes the accompanying prospectus to the extent it contains information different from or additional to the information in that prospectus.

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus. The second part is the accompanying prospectus, which gives more general information and disclosure. To the extent the information contained in this prospectus supplement differs from the information contained in the accompanying prospectus, the information in this prospectus supplement shall control. Please carefully read this prospectus supplement and the accompanying prospectus together with any exhibits and the additional information described under “Available Information” and in the “Summary” and “Risk Factors” sections before you make an investment decision.

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FEES AND EXPENSES

The following table is intended to assist you in understanding the costs and expenses that you will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus supplement and the accompanying prospectus contains a reference to fees or expenses paid by “you”, “NMFC”, the “Operating Company”, or “us” or that “we”, “NMFC”, or the “Operating Company” will pay fees or expenses, stockholders will indirectly bear such fees or expenses through NMFC’s investment in the Operating Company.

Example

The following example, required by the SEC, demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in NMFC’s common stock. In calculating the following expense amounts, we have assumed that our borrowings and annual operating expenses would remain at the levels set forth in the table above. See Note 6 below for additional information regarding certain assumptions regarding our level of leverage.

The example and the expenses in the tables above should not be considered a representation of future expenses, and actual expenses may be greater or less than those shown.

While the example assumes, as required by the applicable rules of the SEC, a 5.0% annual return, our performance will vary and may result in a return greater or less than 5.0%. The incentive fee under the Investment Management Agreement, which, assuming a 5.0% annual return, would either not be payable or would have an insignificant impact on the expense amounts shown above, is not included in the example. The above illustration assumes that we will not realize any capital gains (computed net of all realized capital losses and unrealized capital depreciation) in any of the indicated time periods. If we achieve sufficient returns on our investments, including through the realization of capital gains, to trigger an incentive fee of a material amount, our expenses and returns to our investors would be higher. For example, if we assumed that we received our 5.0% annual return completely in the form of net realized capital gains on our investments, computed net of all cumulative

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unrealized depreciation on our investments, the projected dollar amount of total cumulative expenses set forth in the above illustration would be as follows:

The example assumes a sales load of 4.0%. In addition, while the examples assume reinvestment of all distributions at net asset value, participants in NMFC’s dividend reinvestment plan will receive a number of shares of NMFC’s common stock determined by dividing the total dollar amount of the distribution payable to a participant by the market price per share of NMFC’s common stock at the close of trading on the dividend payment date. The market price per share of NMFC’s common stock may be at, above or below net asset value. See “Dividend Reinvestment Plan” in the accompanying prospectus for additional information regarding the dividend reinvestment plan.

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SELECTED FINANCIAL AND OTHER DATA

The selected financial data should be read in conjunction with the respective financial statements and related combined notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in this prospectus. Financial information for the years ended December 31, 2011, December 31, 2010, December 31, 2009 and for the period October 29, 2008 (commencement of operations) to December 31, 2008 has been derived from our financial statements that were audited by Deloitte & Touche, LLP, an independent registered public accounting firm. The financial information for the nine months ended September 30, 2012 was derived from our unaudited financial statements and related notes. In the opinion of management, all adjustments, consisting solely of normal recurring accruals, considered necessary for the fair presentation of financial statements for the interim periods, have been included. Our results for the interim period may not be indicative of our results for the full year. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations” elsewhere in this prospectus supplement and “Senior Securities” in the accompanying prospectus for more information.

(in thousands except shares and per share data)

N/A—Fund was not unitized as of December 31, 2010, December 31, 2009 and December 31, 2008.

NM—Total return from commencement of operations through December 31, 2008 was deemed not meaningful due to the scaling of operations during this short time period.

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(in thousands except shares and per share data)

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SELECTED QUARTERLY FINANCIAL DATA

The following table sets forth certain quarterly financial data for the quarters ended September 30, 2012, June 30, 2012 and March 31, 2012 and for each of the quarters for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009 of the Operating Company and for the quarters ended September 30, 2012, June 30, 2012 and March 31, 2012 and for each of the quarters from May 19, 2011 (commencement of operations) through December 31, 2011 of NMFC. This data is derived from our unaudited financial statements. Results for any quarter are not necessarily indicative of results for the full year or for any future quarter.

The below selected quarterly financial data is for the Operating Company.

(in thousands except for per unit data)

N/A—Not applicable, as the Operating Company was not unitized until May 19, 2011.

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The below selected quarterly financial data is for NMFC.

(in thousands except for per share data)

N/A—Not applicable, as NMFC did not commence operations until May 19, 2011.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement contains forward-looking statements that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estimates and projections about us, the Operating Company’s current and prospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates”, “expects”, “intends”, “plans”, “believes”, “seeks”, “estimates”, “would”, “should”, “targets”, “projects”, and variations of these words and similar expressions are intended to identify forward-looking statements. The forward-looking statements contained in this prospectus supplement involve risks and uncertainties, including statements as to:

These statements are not guarantees of future performance and are subject to risks, uncertainties, and other factors, some of which are beyond our control and difficult to predict and could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements, including without limitation:

Although we believe that the assumptions on which these forward-looking statements are based are reasonable, any of those assumptions could prove to be inaccurate, and as a result, the forward-looking statements based on those assumptions also could be inaccurate. Important assumptions include the Operating Company’s ability to originate new loans and investments, certain margins and

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levels of profitability and the availability of additional capital. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus supplement should not be regarded as a representation by us that our plans and objectives will be achieved. These risks and uncertainties include those described or identified in “Risk Factors” and elsewhere in this prospectus supplement and the accompanying prospectus. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this prospectus supplement. However, we will update this prospectus supplement to reflect any material changes to the information contained herein. The forward-looking statements and projections contained in this prospectus supplement are excluded from the safe harbor protection provided by Section 27A of the Securities Act of 1933, as amended, or the Securities Act.

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CAPITALIZATION

The following table sets forth our capitalization as of September 30, 2012:

You should read this table together with “Use of Proceeds” and financial statements and related notes thereto included elsewhere in this prospectus supplement and the accompanying prospectus.

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USE OF PROCEEDS

We estimate that we will receive net proceeds from the sale of the 3,000,000 shares of NMFC’s common stock in this offering of approximately $43.5 million (using the last reported closing price of NMFC’s common stock on November 30, 2012 of $15.18 per share), after deducting estimated offering expenses of approximately $0.2 million payable by the Operating Company and underwriting discounts and commissions of approximately $1.8 million. In addition, the Investment Adviser has agreed to bear an additional $             of commissions in connection with this offering, which will not be subject to reimbursement by either NMFC or the Operating Company.

The Operating Company intends to use the net proceeds from this offering primarily for new investments in portfolio companies in accordance with the Operating Company’s investment objective and strategies described in this prospectus supplement and the accompanying prospectus. The Operating Company may also use a portion of the net proceeds for other general corporate purposes, including to temporarily repay indebtedness (which will be subject to reborrowing), and other working capital needs. The Operating Company is continuously identifying, reviewing and, to the extent consistent with its investment objective, funding new investments. As a result, we typically raise capital as we deem appropriate to fund such new investments.

We expect the Operating Company to substantially invest the net proceeds of this offering by the end of the calendar year, depending on the availability of attractive opportunities and market conditions. However, we can offer no assurance that we will be able to achieve this goal.

Proceeds not immediately used for new investments or the temporary repayment of debt will be invested primarily in cash, cash equivalents, U.S. government securities and other high-quality investments that mature in one year or less from the date of investment. These temporary investments are expected to provide a lower net return than we hope to achieve from the Operating Company’s target investments.

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PRICE RANGE OF COMMON STOCK AND DISTRIBUTIONS

NMFC’s common stock is traded on the New York Stock Exchange (“NYSE”) under the symbol “NMFC”. The following table sets forth the net asset value (“NAV”) per share of NMFC’s common stock, the high and low closing sale price for NMFC’s common stock, the closing sale price as a percentage of NAV and the quarterly dividend distributions per share for each fiscal quarter since NMFC’s IPO on May 19, 2011.

On November 30, 2012, the last reported sales price of NMFC’s common stock was $15.18 per share. As of September 30, 2012, the Operating Company had two record holders, which were NMFC and AIV Holdings, whereas NMFC had approximately 17 stockholders of record and approximately three beneficial owners whose shares are held in the names of brokers, dealers, funds, trusts and clearing agencies. The Operating Company is not a publicly traded entity.

Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that NMFC’s shares of common stock will trade at a discount from net asset value or at premiums that are unsustainable over the long term are separate and distinct from the risk that our net asset value will decrease. Since NMFC’s initial public offering on May 19, 2011, NMFC’s shares of common stock have traded at times at a discount to the net assets attributable to those shares. As of November 30, 2012, NMFC’s shares of common stock traded at a premium of approximately 7.7% of the net asset value attributable to those shares as of September 30, 2012. It is not possible to predict whether the shares offered hereby will trade at, above, or below net asset value.

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Since NMFC is a holding company, distributions will be paid on NMFC’s common stock from distributions received from the Operating Company. The Operating Company intends to make distributions to its unit holders that will be sufficient to enable NMFC to pay quarterly distributions to NMFC’s stockholders and to maintain NMFC’s status as a regulated investment company. NMFC intends to distribute approximately its entire portion of the Operating Company’s Adjusted Net Investment Income on a quarterly basis and substantially its entire portion of the Operating Company’s taxable income on an annual basis, except that they may retain certain net capital gains for reinvestment.

NMFC has adopted an “opt out” dividend reinvestment plan on behalf of its stockholders, whereas NMFC stockholders’ cash dividends will be automatically reinvested in additional shares of NMFC’s common stock, unless the stockholder elects to receive cash. Cash dividends reinvested in additional shares of NMFC’s common stock will be automatically reinvested by NMFC into additional units of the Operating Company.

NMFC applies the following in implementing the dividend reinvestment plan. If the price at which newly issued shares are to be credited to stockholders’ accounts is greater than 110.0% of the last determined net asset value of the shares, NMFC will use only newly issued shares to implement its dividend reinvestment plan. Under such circumstances, the number of shares to be issued to a stockholder is determined by dividing the total dollar amount of the distribution payable to such stockholder by the market price per share of NMFC’s common stock on the NYSE on the distribution payment date. Market price per share on that date will be the closing price for such shares on the NYSE or, if no sale is reported for such day, the average of their electronically reported bid and asked prices. If NMFC uses newly issued shares to implement the plan, NMFC will receive, on a one-for-one basis, additional units of the Operating Company in exchange for cash distributions that are reinvested in shares of NMFC’s common stock under the dividend reinvestment plan.

If the price at which newly issued shares are to be credited to stockholders’ accounts is less than 110.0% of the last determined net asset value of the shares, NMFC will either issue new shares or instruct the plan administrator to purchase shares in the open market to satisfy the additional shares required. Shares purchased in open market transactions by the plan administrator will be allocated to a stockholder based on the average purchase price, excluding any brokerage charges or other charges, of all shares of common stock purchased in the open market. The number of shares of NMFC’s common stock to be outstanding after giving effect to payment of the distribution cannot be established until the value per share at which additional shares will be issued has been determined and elections of NMFC’s stockholders have been tabulated.

The following table reflects the cash distributions, including dividends and returns of capital, if any, per unit/share that have been declared by the Operating Company’s board of directors, and subsequently NMFC’s board of directors, since NMFC’s IPO:

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Tax characteristics of all dividends paid by NMFC are reported to stockholders on Form 1099 after the end of the calendar year. Future quarterly dividends, if any, for the New Mountain Finance Entities will be determined by their respective board of directors.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The information contained in this section should be read in conjunction with the Selected Financial and Other Data and our Financial Statements and notes thereto appearing elsewhere in this prospectus supplement and the accompanying prospectus. In addition to historical information, the following discussion and other parts of this prospectus supplement and the accompanying prospectus contain forward-looking information that involves risks and uncertainties. Our actual results could differ materially from those anticipated by such forward-looking information due to the factors discussed under “Risk Factors” appearing in the accompanying prospectus and “Cautionary Statement Regarding Forward-Looking Statements” appearing elsewhere in this prospectus supplement.

Overview

The Operating Company is a Delaware limited liability company. The Operating Company is externally managed and has elected to be treated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “1940 Act”). As such, The Operating Company is obligated to comply with certain regulatory requirements. The Operating Company intends to be treated as a partnership for federal income tax purposes for so long as it has at least two members.

The Operating Company is externally managed by the Investment Adviser. New Mountain Finance Administration, L.L.C. (the “Administrator”) provides the administrative services necessary for operations. The Investment Adviser and Administrator are wholly-owned subsidiaries of New Mountain Capital (defined as New Mountain Capital Group, L.L.C. and its affiliates). New Mountain Capital is a firm with a track record of investing in the middle market and with assets under management (which includes amounts committed, not all of which have been drawn down and invested to date) totaling approximately $9.0 billion as of September 30, 2012. New Mountain Capital focuses on investing in defensive growth companies across its private equity, public equity, and credit investment vehicles. The Operating Company, formerly known as New Mountain Guardian (Leveraged), L.L.C., was originally formed as a subsidiary of New Mountain Guardian AIV, L.P. (“Guardian AIV”) by New Mountain Capital in October 2008. Guardian AIV was formed through an allocation of approximately $300.0 million of the $5.1 billion of commitments supporting New Mountain Partners III, L.P., a private equity fund managed by New Mountain Capital. In February 2009, New Mountain Capital formed a co-investment vehicle, New Mountain Guardian Partners, L.P., comprising $20.4 million of commitments. New Mountain Guardian (Leveraged), L.L.C. and New Mountain Guardian Partners, L.P., together with their respective direct and indirect wholly- owned subsidiaries, are defined as the “Predecessor Entities”.

NMFC is a Delaware corporation that was originally incorporated on June 29, 2010. NMFC is a closed-end, non-diversified management investment company that has elected to be treated as a BDC under the 1940 Act. As such, NMFC is obligated to comply with certain regulatory requirements. NMFC has elected to be treated, and intends to comply with the requirements to continue to qualify annually, as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended, (the “Code”).

AIV Holdings is a Delaware corporation that was originally incorporated on March 11, 2011. Guardian AIV, a Delaware limited partnership, is AIV Holdings’ sole stockholder. AIV Holdings is a closed-end, non-diversified management investment company that has elected to be treated as a BDC under the 1940 Act. As such, AIV Holdings is obligated to comply with certain regulatory requirements. AIV Holdings has elected to be treated, and intends to comply with the requirements to continue to qualify annually, as a RIC under the Code.

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On May 19, 2011, NMFC priced its initial public offering (the “IPO”) of 7,272,727 shares of common stock at a public offering price of $13.75 per share. Concurrently with the closing of the IPO and at the public offering price of $13.75 per share, NMFC sold an additional 2,172,000 shares of its common stock to certain executives and employees of, and other individuals affiliated with, New Mountain Capital in a concurrent private placement (the “Concurrent Private Placement”). Additionally, 1,252,964 shares were issued to the limited partners of New Mountain Guardian Partners, L.P. at that time for their ownership interest in the Predecessor Entities. In connection with NMFC’s IPO and through a series of transactions, the Operating Company owns all of the operations of the Predecessor Entities, including all of the assets and liabilities related to such operations.

On July 10, 2012, NMFC’s shelf registration statement became effective. On July 17, 2012, NMFC completed a public offering of 5,250,000 shares of its common stock at a public offering price of $14.35 per share. In connection with the offering, the underwriters purchased an additional 676,802 shares with the exercise of the overallotment option to purchase up to an additional 787,500 shares of common stock. As a result of this public offering, NMFC and AIV Holdings owned approximately 45.1% and 54.9%, respectively, of the units of the Operating Company.

On September 28, 2012, NMFC completed an underwritten secondary public offering of 4,000,000 shares of its common stock at a public offering price of $15.00 per share on behalf of a selling stockholder, AIV Holdings. No shares were sold by NMFC, and it did not receive any proceeds from this secondary public offering. The Operating Company and NMFC did not bear any expenses in connection with this offering. The offering expenses were borne by the selling stockholder, AIV Holdings. After completion of this underwritten secondary public offering, NMFC and AIV Holdings owned approximately 56.0% and 44.0%, respectively, of the units of the Operating Company.

NMFC and AIV Holdings are holding companies with no direct operations of their own, and their sole asset is their ownership in the Operating Company. NMFC and AIV Holdings each entered into a joinder agreement with respect to the Limited Liability Company Agreement, as amended and restated, of the Operating Company, pursuant to which NMFC and AIV Holdings were admitted as members of the Operating Company. NMFC acquired from the Operating Company, with the gross proceeds of the IPO and the Concurrent Private Placement, common membership units (“units”) of the Operating Company (the number of units are equal to the number of shares of NMFC’s common stock sold in the IPO and the Concurrent Private Placement). Additionally, NMFC received units of the Operating Company equal to the number of shares of common stock of NMFC issued to the limited partners of New Mountain Guardian Partners, L.P. Guardian AIV was the parent of the Operating Company prior to the IPO and, as a result of the transactions completed in connection with the IPO, obtained units in the Operating Company. Guardian AIV contributed its units in the Operating Company to its newly formed subsidiary, AIV Holdings, in exchange for common stock of AIV Holdings. AIV Holdings has the right to exchange all or any portion of its units in the Operating Company for shares of NMFC’s common stock on a one-for-one basis.

As part of the third quarter 2012 dividend payment, NMFC issued an additional 66,142 shares in conjunction with its dividend reinvestment plan at a price of $14.82. As of September 30, 2012, NMFC and AIV Holdings own approximately 56.1% and 43.9%, respectively, of the units of the Operating Company.

The current structure was designed to generally prevent NMFC from being allocated taxable income with respect to unrecognized gains that existed at the time of the IPO in the Predecessor Entities’ assets, and rather such amounts would be allocated generally to AIV Holdings. The result is that any distributions made to NMFC’s stockholders that are attributable to such gains generally will not be treated as taxable dividends but rather as return of capital.

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The diagram below depicts our current organizational structure (percentages are prior to this offering).

The Operating Company’s investment objective is to generate current income and capital appreciation through the sourcing and origination of debt securities at all levels of the capital structure, including first and second lien debt, notes, bonds and mezzanine securities. In some cases, the Operating Company’s investments may also include equity interests. The primary focus is in the debt of defensive growth companies, which are defined as generally exhibiting the following characteristics: (i) sustainable secular growth drivers, (ii) high barriers to competitive entry, (iii) high free cash flow after capital expenditure and working capital needs, (iv) high returns on assets and (v) opportunities for niche market dominance.

As of September 30, 2012, the Operating Company’s net asset value was $520.4 million and its portfolio had a fair value of approximately $858.9 million in 58 portfolio companies, with a weighted average Yield to Maturity of approximately 9.9%. This Yield to Maturity calculation assumes that all investments not on non-accrual are purchased at fair value on September 30, 2012 and held until their respective maturities with no prepayments or losses and exited at par at maturity. The actual yield to maturity may be higher or lower due to the future selection of the London Interbank Offered Rate (“LIBOR”) contracts by the individual companies in the Operating Company’s portfolio or other factors.

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Recent Developments

On November 6, 2012, the Operating Company’s board of directors, and subsequently NMFC’s board of directors, declared a fourth quarter 2012 distribution of $0.34 per unit/share payable on December 28, 2012 to holders of record as of December 14, 2012.

Critical Accounting Policies

The preparation of financial statements and related disclosures in conformity with generally accepted accounting principles in the United States (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and revenues and expenses during the periods reported. Actual results could materially differ from those estimates. We have identified the following items as critical accounting policies.

Basis of Accounting

The Operating Company consolidates its wholly-owned subsidiary, NMF SLF. NMFC does not consolidate the Operating Company. NMFC applies investment company master-feeder financial statement presentation, as described in Accounting Standards Codification 946, Financial Services—Investment Companies, (“ASC 946”) to their interest in the Operating Company. NMFC observes that it is industry practice to follow the presentation prescribed for a Master Fund-Feeder Fund structure in ASC 946 in instances in which a Master Fund is owned by more than one feeder fund and that such presentation provides stockholders of NMFC with a clearer depiction of their investment in the Master Fund.

Valuation and Leveling of Portfolio Investments

The Operating Company conducts the valuation of assets, pursuant to which its net asset value, and, consequently, NMFC’s net asset value is determined, at all times consistent with GAAP and the 1940 Act.

The Operating Company values its assets on a quarterly basis, or more frequently if required under the 1940 Act. In all cases, the Operating Company’s board of directors is ultimately and solely responsible for determining the fair value of its portfolio investments on a quarterly basis in good faith, including investments that are not publicly traded, those whose market prices are not readily available, and any other situation where its portfolio investments require a fair value determination. Security transactions are accounted for on a trade date basis. The Operating Company’s quarterly valuation procedures are set forth in more detail below:

(1) Investments for which market quotations are readily available on an exchange are valued at such market quotations based on the closing price indicated from independent pricing services.

(2) Investments for which indicative prices are obtained from various pricing services and/or brokers or dealers are valued through a multi-step valuation process, as described below, to determine whether the quote(s) obtained is representative of fair value in accordance with GAAP.

a. Bond quotes are obtained through independent pricing services. Internal reviews are performed by the investment professionals of the Investment Adviser to ensure that the quote obtained is representative of fair value in accordance with GAAP and if so, the quote is used. If the Investment Adviser is unable to sufficiently validate the quote(s) internally and if the

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investment’s par value exceeds the materiality threshold, the investment is valued similarly to those assets with no readily available quotes (see (3) below);

b. For investments other than bonds, the investment professionals of the Investment Adviser look at the number of quotes readily available and perform the following:

i. Investments for which two or more quotes are received from a pricing service are valued using the mean of the mean of the bid and ask of the quotes obtained;

ii. Investments for which one quote is received from a pricing service are validated internally. The investment professionals of the Investment Adviser analyze the market quotes obtained using an array of valuation methods (further described below) to validate the fair value. If the Investment Adviser is unable to sufficiently validate the quote internally and if the investment’s par value exceeds the materiality threshold, the investment is valued similarly to those assets with no readily available quotes (see (3) below).

(3) Investments for which quotations are not readily available through exchanges, pricing services, brokers, or dealers are valued through a multi-step valuation process:

a. Each portfolio company or investment is initially valued by the investment professionals of the Investment Adviser responsible for the credit monitoring;

b. Preliminary valuation conclusions will then be documented and discussed with the Operating Company’s senior management;

c. If an investment falls into (3) above for four consecutive quarters and if the investment’s par value exceeds the materiality threshold, then at least once each fiscal year, the valuation for each portfolio investment for which the investment professionals of the Investment Adviser do not have a readily available market quotation will be reviewed by an independent valuation firm engaged by the Operating Company’s board of directors.

d. Also, when deemed appropriate by the Operating Company’s management, an independent valuation firm may be engaged to review and value investment(s) of a portfolio company, without any preliminary valuation being performed by the Investment Adviser. The investment professionals of the Investment Adviser will review and validate the value provided.

Valuation methods may include comparisons of financial ratios of the portfolio companies that issued such private securities to peer companies that are public, the nature of and the realizable value of any collateral, the portfolio company’s earnings, discounted cash flows, the ability to make payments, the markets in which the portfolio company conducts business, and other relevant factors, including available market data such as relevant and applicable market trading and transaction comparables; applicable market yields and multiples; security covenants; call protection provisions; information rights; comparable merger and acquisition transactions; and the principal market and enterprise values. When an external event such as a purchase transaction, public offering or subsequent sale occurs, we will consider the pricing indicated by the external event to corroborate the private valuation.

The values assigned to investments are based upon available information and do not necessarily represent amounts which might ultimately be realized, since such amounts depend on future circumstances and cannot be reasonably determined until the individual positions are liquidated. Due to the inherent uncertainty of determining the fair value of investments that do not have a readily available market value, the fair value of certain investments may fluctuate from period to period.

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GAAP fair value measurement guidance classifies the inputs used in measuring fair value into three levels as follows:

Level I—Quoted prices (unadjusted) are available in active markets for identical investments and the Operating Company has the ability to access such quotes as of the reporting date. The type of investments which would generally be included in Level I include active exchange-traded equity securities and exchange-traded derivatives. As required by Accounting Standards Codification 820, Fair Value Measurements and Disclosures (“ASC 820”), the Operating Company, to the extent that we hold such investments, does not adjust the quoted price for these investments, even in situations where the Operating Company holds a large position and a sale could reasonably impact the quoted price.

Level II—Pricing inputs are observable for the investments, either directly or indirectly, as of the reporting date, but are not the same as those used in Level I. Level II inputs include the following:

Level III—Pricing inputs are unobservable for the investment and include situations where there is little, if any, market activity for the investment.

The inputs into the determination of fair value require significant judgment or estimation by management. A review of the fair value hierarchy classifications is conducted on a quarterly basis. Changes in the observability of valuation inputs may result in the reclassification of certain investments within the fair value hierarchy from period to period.

The following table summarizes the levels in the fair value hierarchy that the Operating Company’s portfolio investments fall into as of September 30, 2012: