NATURAL GAS SERVICES GROUP INC

The results of operations attributable to the Flatrock Acquisition have been included in our unaudited Condensed Consolidated Financial Statements from the Acquisition Date through September 30, 2026. Total revenue attributable to the net assets acquired from Flatrock for the three months ended September 30, 2026, and from the Acquisition Date through September 30, 2026, was $10.4 million and $12.6 million, respectively, and pre-tax earnings attributable to the assets acquired and liabilities assumed for the three months ended September 30, 2026, and the Acquisition Date through September 30, 2026, was $1.7 million and $2.5 million, respectively.

Transaction costs

In connection with the Flatrock Acquisition, we engaged certain advisors and consultants to assist us with various activities to develop, execute, and report the transaction. A substantial portion of costs, primarily legal and diligence, were incurred during the three months ended June 30, 2026, and additional transaction costs were incurred during the third quarter of 2026, primarily attributable to advisory costs associated with the valuation, purchase price allocation, working capital adjustment and review, and financial reporting. The following table summarizes transaction costs, primarily legal and diligence, directly attributable to the Flatrock Acquisition incurred during the year-to-date period ended September 30, 2026, which was recorded in selling, general and administrative expenses:

(1) Includes legal, business diligence, financial advisory, and other consulting fees.

Unaudited Pro forma Financial Information

The unaudited supplemental pro forma financial information for the three and nine months ended September 30, 2026 and 2025 was derived by adjusting our historical financial statements in order to give effect to the Flatrock assets acquired and liabilities assumed as though the Flatrock Acquisition occurred as of January 1, 2025 and reflects the following:

•the application of our accounting policies to reflect the changes in depreciation and amortization attributable to the acquired rental equipment, property and equipment and intangible assets;

•the incremental interest expense resulting from borrowings under the Credit Facility to fund the cash component of the consideration transferred;

•the income tax effects of the adjustments described above based on our blended statutory tax rate.

The unaudited pro forma financial information presented below is presented for informational purposes only and is not necessarily indicative of the results of operations that would have occurred had the Flatrock Acquisition been consummated at the beginning of the period presented nor is it necessarily indicative of our future results of operations. Future results may vary significantly from the results reflected in this unaudited pro forma financial information.