SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 15)

New Mountain Finance Corporation

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

Steven B. Klinsky
New Mountain Finance Corporation, 1633 Broadway, 48th Floor
New York, NY, 10019
(212) 720-0300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

03/10/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. Checkbox not checked

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

KLINSKY STEVEN B

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 9,800,060.91
8	Shared Voting Power 2,530,093.00
9	Sole Dispositive Power 9,800,060.91
10	Shared Dispositive Power 2,530,093.00

Aggregate amount beneficially owned by each reporting person

12,330,153.91

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

12.52 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

* Of the shares shown above, the Steven B. Klinsky 2008 Long Term Trust holds 1,465,110.00 shares, the Steven B. Klinsky Non-GST Exempt Trust holds 1,020,267.00 shares, the Steven B, Klinsky 2024 Revocable Trust ("2024 Trust 1") holds 5,370,858.00 shares, the Steven B, Klinsky 2024 Revocable Trust ("2024 Trust 2") holds 3,457,379.00 shares, and the Steven B. Klinsky 2024 Revocable Trust ("2024 Trust 3") holds 855,000.00 shares. Mr. Klinsky is the sole trustee of 2024 Trust 1, 2024 Trust 2 and 2024 Trust 3. Of the shares shown above, an immediate family member of the Reporting Persons holds 16.00 shares directly, and immediate family members of the Reporting Persons collectively hold 44,700 shares indirectly through a trust, which the Reporting Persons disclaim beneficial ownership of except to the extent of their pecuniary interest therein.

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

STEVEN B. KLINSKY 2008 LONG TERM TRUST

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,465,110.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,465,110.00

Aggregate amount beneficially owned by each reporting person

1,465,110.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

1.49 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

STEVEN B. KLINSKY NON-GST EXEMPT TRUST

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,020,267.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,020,267.00

Aggregate amount beneficially owned by each reporting person

1,020,267.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

1.04 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 1)

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 5,370,858.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 5,370,858.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

5,370,858.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

5.45 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 2)

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 3,457,379.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 3,457,379.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

3,457,379.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

3.51 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 3)

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 855,000.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 855,000.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

855,000.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.87 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

Name of reporting person

Weinstein Adam B.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

PF, OO

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 738,856.32
8	Shared Voting Power 0.00
9	Sole Dispositive Power 738,856.32
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

738,856.32

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.75 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

Item 1.

Security and Issuer

(a)

Title of Class of Securities:

Common Stock, par value $0.01 per share

(b)

Name of Issuer:

New Mountain Finance Corporation

(c)

Address of Issuer's Principal Executive Offices:

1633 Broadway, 48th Floor, New York, NEW YORK , 10019.

Item 1 Comment:

This Amendment No. 15 amends and supplements the statement on Schedule 13D, filed on May 31, 2011, as amended by Amendment No. 1 thereto filed on August 9, 2011, Amendment No. 2 thereto filed on October 3, 2012, Amendment No. 3 thereto filed on October 23, 2012, Amendment No. 4 thereto filed March 28, 2013, Amendment No. 5 thereto filed on June 28, 2013, Amendment No. 6 thereto filed on July 18, 2013, Amendment No. 7 thereto filed on November 1, 2013, Amendment No. 8 thereto filed on February 18, 2014, Amendment No. 9 filed on October 15, 2015, Amendment No. 10 filed on March 4, 2016, Amendment No. 11 filed on November 1, 2019, Amendment No. 12 filed on June 5, 2020, Amendment No. 13 filed on November 26, 2024, and Amendment No. 14 filed on March 3, 2026 (collectively, the "Schedule 13D"), initially filed by New Mountain Investments III, L.L.C., a Delaware limited liability company, New Mountain Guardian AIV, L.P., a Delaware limited partnership, New Mountain Finance AIV Holdings Corporation, a Delaware corporation ("AIV Holdings"), New Mountain Guardian Partners, L.P. , a Delaware limited partnership ("Guardian Partners"), New Mountain Guardian GP, L.L.C., a Delaware limited liability company ("Guardian GP"), Steven B. Klinsky, the Steven B. Klinsky Trust, the Steven B. Klinsky Non-GST Exempt Trust, and Adam J. Collins with respect to the common stock, par value $0.01 per share ("Common Stock"), of New Mountain Finance Corporation, a Delaware corporation (the "Issuer"). Capitalized terms used herein but not defined shall have the meanings ascribed thereto in the Schedule 13D. Except as herein amended or supplemented, all other information in the Schedule 13D is as set forth therein. The address of the principal executive offices of the Issuer is 1633 Broadway, 48th Floor, New York, NY 10019.

Item 2.

Identity and Background

(a)

This Statement is being filed by Steven B. Klinsky, the Steven B. Klinsky 2008 Long Term Trust (the "2008 Trust"), the Steven B. Klinsky Non-GST Exempt Trust (the "Exempt Trust"), the Steven B. Klinsky 2024 Revocable Trust (the "2024 Trust 1"), the Steven B. Klinsky 2024 Revocable Trust (the "2024 Trust 2"), the Steven B. Klinsky 2024 Revocable Trust (the "2024 Trust 3") and Adam B. Weinstein (collectively, the "Reporting Persons"). Neither the present filing nor anything contained herein shall be construed as an admission that (i) any Reporting Person constitutes a "person" for any purposes other than Section 13(d) of the Act, (ii) any of the Reporting Persons are, for purposes of Section 13(d) or Section 16 of the Act or otherwise, a member of a group, or (iii) any of the Reporting Persons are, for the purposes of Sections 13(d) of the Act, the beneficial owner of any securities other than securities directly owned by such Reporting Persons. The Reporting Persons have entered into a joint filing agreement, dated as of October 15, 2015, a copy of the which was attached as Exhibit 99.1 to Amendment No. 9 on October 15, 2015.

(b)

The principal business address of each of the Reporting Persons is 1633 Broadway, 48th Floor, New York, NY 10019

(c)

Mr. Klinsky is principally engaged in the business of serving as the Chief Executive Officer of New Mountain Capital Group L.P. ("New Mountain Capital") and is the Chairman of the Board of Directors of the Issuer. Each of the 2008 Trust, the Exempt Trust, the 2024 Trust 1, the 2024 Trust 2 and the 2024 Trust 3 is a New York trust. Mr. Klinsky is the investment trustee and Adam Weinstein is the trustee of the 2008 Trust and the Exempt Trust. Mr. Klinsky is the trustee of the 2024 Trust 1, the 2024 Trust 2 and the 2024 Trust 3. Mr. Weinstein is a Managing Director of New Mountain Capital. The principal business address for New Mountain Capital and the Issuer is 1633 Broadway, 48th Floor, New York, NY 10019.

(d)

None of the Reporting Persons during the last five years has been convicted in a criminal proceeding (excluding traffic violations and similar misdemeanors).

(e)

None of the Reporting Persons during the last five years has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which any such person was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f)

Mr. Klinsky is a citizen of the United States of America. Each of the 2008 Trust, the Exempt Trust, the 2024 Trust 1, the 2024 Trust 2 and the 2024 Trust 3 is a New York trust. Mr. Weinstein is a citizen of the United States of America.

Item 3.

Source and Amount of Funds or Other Consideration

Since March 3, 2026 through March 11, 2026, Steven B. Klinsky, the 2008 Trust, the Exempt Trust, the 2024 Trust 1, the 2024 Trust 2, and the 2024 Trust 3 acquired, either in open market purchases or through the Issuer's dividend reinvestment plan, an aggregate of 1,175,273 shares of the Issuer's Common Stock using Mr. Klinsky personal funds, which were not borrowed or otherwise obtained for the purpose of acquiring the Issuer's Common Stock. Since March 3, 2026 through March 11, 2026, Adam B. Weinstein did not acquire any shares of the Issuer's Common Stock.

Item 4.

Purpose of Transaction

Mr. Klinsky, the 2008 Trust, the Exempt Trust, the 2024 Trust 1, the 2024 Trust 2, the 2024 Trust 3, and Mr. Weinstein purchased the shares of Common Stock based on the belief that the shares of Common Stock, when purchased, represented an attractive investment opportunity.

Item 5.

Interest in Securities of the Issuer

(a)

The aggregate number and percentage of the class of securities identified pursuant to Item 1 beneficially owned by each Reporting Person is stated in Items 11 and 13 on the cover page(s) hereto.

(b)

The number of shares as to which the Reporting Persons have sole power to vote or dispose of is stated in Items 7 and 9 on the cover page(s) hereto.

(c)

Other than the open market purchases of the shares of the Issuer's Common Stock by Mr. Weinstein and Mr. Klinsky described below, there have been no transactions in the Issuer's Common Stock effected by the Reporting Persons since the most recent Amendment No. 14 filed on March 3, 2026. On March 3, 2026, the Steven B. Klinsky 2008 Long Term Trust purchased 83,498 shares at an average price per share of $7.9426. On March 3, 2026, 2024 Trust 1 purchased 166,997 shares at an average price per share of $7.9426. On March 4, 2026, the Steven B. Klinsky 2008 Long Term Trust purchased 62,301 shares at an average price per share of $8.1671. On March 4, 2026, 2024 Trust 1 purchased 124,604 shares at an average price per share of $8.1671. On March 5, 2026, the Steven B. Klinsky 2008 Long Term Trust purchased 79,291 shares at an average price per share of $8.10. On March 5, 2026, 2024 Trust 1 purchased 158,582 shares at an average price per share of $8.10. On March 10, 2026, the Steven B. Klinsky 2008 Long Term Trust purchased 74,586 shares at an average price per share of $8.05. On March 10, 2026, 2024 Trust 1 purchased 149,172 shares at an average price per share of $8.05. On March 11, 2026, the Steven B. Klinsky 2008 Long Term Trust purchased 92,080 shares at an average price per share of $8.05. On March 11, 2026, 2024 Trust 1 purchased 184,162 shares at an average price per share of $8.05.

(d)

Of the shares of Common Stock described in this Schedule 13D, 16 shares are held directly and 44,700 shares are held indirectly through a trust by immediate family members of the Reporting Persons. The Reporting Persons disclaim beneficial ownership of these shares except to the extent of their pecuniary interest therein. The immediate family member has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares of Common Stock of the Issuer that they hold directly.

(e)

Not applicable

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

KLINSKY STEVEN B

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky
Date:	03/12/2026

STEVEN B. KLINSKY 2008 LONG TERM TRUST

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky, Authorized Person
Date:	03/12/2026

STEVEN B. KLINSKY NON-GST EXEMPT TRUST

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky, Authorized Person
Date:	03/12/2026

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 1)

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky, Authorized Person
Date:	03/12/2026

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 2)

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky, Authorized Person
Date:	03/12/2026

STEVEN B. KLINSKY 2024 REVOCABLE TRUST (2024 TRUST 3)

Signature:	/s/ Steven B. Klinsky
Name/Title:	Steven B. Klinsky, Authorized Person
Date:	03/12/2026

Weinstein Adam B.

Signature:	/s/ Adam B. Weinstein
Name/Title:	Adam B. Weinstein
Date:	03/12/2026

Amendment: SEC Form SCHEDULE 13D/A filed by New Mountain Finance Corporation