UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K/A

(Amendment No. 1)

Current Report
Pursuant to Section 13 or 15(d)
of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): September 19, 2025 (September 12, 2025)

Mach Natural Resources LP

(Exact name of registrant as specified in its charter)

(405) 252-8100

Registrant’s telephone number, including area code

Not applicable.

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Explanatory Note

Item 2.01. Completion of Acquisition or Disposition of Assets.

This Amendment amends Item 2.01 of the Original Report to correct the purchase price for the IKAV Assets to $758.9 million, which was comprised of (i) cash in the amount of $349.0 million and (ii) 30,611,264 Common Units, net of preliminary and customary purchase price adjustments and subject to final post-closing settlement.

Item 9.01. Financial Statements and Exhibits.

(a) Financial statements of businesses acquired.

Sabinal

The audited consolidated balance sheets of Sabinal Energy Operating as of December 31, 2024 and 2023 and the audited consolidated statements of operations, statements of members’ capital and statements of cash flows for each of the years ended December 31, 2024 and 2023, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.1 and are incorporated herein by reference.

The unaudited consolidated balance sheet of Sabinal Energy Operating as of June 30, 2025 and the unaudited consolidated statements of operations, statements of members’ capital and statements of cash flows for each of the six months ended June 30, 2025 and 2024, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.2 and are incorporated herein by reference.

IKAV

The audited statements of financial position of SJ INVESTMENT as of December 31, 2024 and 2023 and the audited statements of operations, statements of changes in member’s capital and statements of cash flows for the year ended December 31, 2024 and for the period from June 27, 2023 to December 31, 2023, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.3 and are incorporated herein by reference.

The unaudited statements of financial position of SJ INVESTMENT as of June 30, 2025 and the unaudited statements of operations and comprehensive income (loss), statements of changes in member’s capital and statements of cash flows for each of the six months ended June 30, 2025 and 2024, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.4 and are incorporated herein by reference.

The audited statements of financial position of SIMCOE as of December 31, 2024 and 2023 and the audited statements of operations and comprehensive income (loss), statements of changes in member’s capital and statements of cash flows for each of the years ended December 31, 2024 and 2023, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.5 and are incorporated herein by reference.

The unaudited statements of financial position of SIMCOE as of June 30, 2025, and the unaudited statements of operations and comprehensive income (loss), statements of changes in member’s capital and statements of cash flows for each of the six months ended June 30, 2025 and 2024, and the related notes thereto, are filed herewith and attached hereto as Exhibit 99.6 and are incorporated herein by reference.

(b) Pro forma financial information.

The unaudited pro forma condensed combined balance sheet of the Company and its subsidiaries as of June 30, 2025, and the unaudited pro forma condensed combined statements of operations for the six months ended June 30, 2025 and for the year ended December 31, 2024, are filed herewith and attached hereto as Exhibit 99.7, and are incorporated herein by reference.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.