New Mountain Finance Corp

Deloitte & Touche LLP 30 Rockefeller PlazaNew York, NY 10112USA Tel: 212 492 4000Fax: 212 489 1687www.deloitte.com

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the shareholders and the Board of Directors of New Mountain Finance Corporation

Opinion on the Consolidated Financial Statements and Financial Highlights

We have audited the accompanying consolidated statements of assets and liabilities of New Mountain Finance Corporation and subsidiaries (the "Company"), including the consolidated schedules of investments, as of December 31, 2023 and 2022, the related consolidated statements of operations, changes in net assets, and cash flows for each of the three years in the period then ended, the consolidated financial highlights for each of the five years in the period then ended, and the related notes. In our opinion, the consolidated financial statements and financial highlights present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations, changes in net assets, and cash flows for each of the three years in the period then ended, and the financial highlights for each of the five years in the period then ended, in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company's internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 26, 2024, expressed an unqualified opinion on the Company's internal control over financial reporting.

Basis for Opinion

These consolidated financial statements and financial highlights are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's consolidated financial statements and financial highlights based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the consolidated financial statements and financial highlights are free of material misstatement, whether due to error or fraud.

Our audits included performing procedures to assess the risks of material misstatement of the consolidated financial statements and financial highlights, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements and financial highlights. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements and financial highlights. Our procedures included confirmation of investments owned as of December 31, 2023 and 2022, by correspondence with the custodian, loan agents, and borrowers; when replies were not received, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current-period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the consolidated financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Fair Value – Investments — Refer to Footnotes 2, 3, and 4 in the consolidated financial statements

Critical Audit Matter Description

The Company invests in debt securities, including first and second lien debt, notes, bonds, mezzanine securities, and equity interests. The Company’s determination of fair value for these investments involves subjective judgments and estimates utilizing a market approach, an income approach, or both approaches, as appropriate. These approaches require management to make judgments and estimates related to significant unobservable inputs including the selection of discount rates and EBITDA or revenue multiples based on multiples of publicly traded comparable companies and comparable transactions.

We identified the valuation of investments as a critical audit matter given the significant judgments made by management to estimate the fair value of certain debt and equity positions. This required a high degree of auditor judgment and extensive audit effort, including the need to involve internal fair value specialists who possess significant valuation experience and modeling expertise, to evaluate the appropriateness of the valuation methodologies and the significant unobservable inputs.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the valuation methodologies and unobservable inputs used by management to estimate the fair value of investments included the following, among others:

•We tested the operating effectiveness of controls over the valuation of investments, including those over the selection of valuation methodologies and development of unobservable inputs.

•We evaluated the reasonableness and consistency of application of the Company's valuation polices over investments, including those surrounding the selection of valuation methodologies and the derivation of valuation inputs.

•With the assistance of our internal fair value specialists, we evaluated the appropriateness of the valuation methodologies and the reasonableness of the significant unobservable inputs.

•With the assistance of our internal fair value specialists, in certain instances, we developed independent fair value estimates and compared our estimates to the Company's estimates.

•We evaluated the impact of current market events and conditions on the selected valuation methodologies and significant unobservable inputs.

/s/ DELOITTE & TOUCHE LLP

February 26, 2024

We have served as the Company's auditor since 2008.