Exhibit 99.4

Unaudited Pro Forma Condensed Combined Financial Data

Defined terms included below have the same meaning as terms defined and included elsewhere in the preliminary prospectus supplement dated October 20, 2024 (the “Preliminary Prospectus Supplement”), except that, unless the context requires otherwise, the term “forward sale agreement” as used herein does not include any additional forward sale agreement that we may enter into in connection with the exercise by the underwriter of its option to purchase additional shares in the offering of shares of common stock contemplated by the Preliminary Prospectus Supplement (the “Offering”).

Introduction

Atlantic Union is providing the following unaudited pro forma condensed combined financial data to aid shareholders in their analysis of the financial aspects of the Merger, the forward sale agreement and its completed acquisition of American National on April 1, 2024 (the “American National acquisition”). See “Summary—Recent Developments— Proposed Acquisition of Sandy Spring Bancorp” for more information on the Merger and see “Underwriting (Conflicts of Interest)—Forward Sale Agreement” for a description of the forward sale agreement. The unaudited pro forma condensed combined financial data has been prepared in accordance with Article 11 of Regulation S-X and should be read in conjunction with the accompanying notes.

The unaudited pro forma condensed combined balance sheet as of June 30, 2024 combines the unaudited consolidated balance sheet of Atlantic Union as of June 30, 2024 with the unaudited consolidated balance sheet of Sandy Spring as of June 30, 2024, giving effect to the Merger and the forward sale agreement as if the Merger had been consummated and the forward sale agreement had been fully physically settled on June 30, 2024.

The unaudited pro forma condensed combined statement of income for the year ended December 31, 2023, combines the audited consolidated statement of income of Atlantic Union for the year ended December 31, 2023, with the audited consolidated statement of income of American National for the year ended December 31, 2023, as well as the audited consolidated statement of income of Sandy Spring for the year ended December 31, 2023, giving effect to the American National acquisition, the Merger and the forward sale agreement as if the American National acquisition and the Merger had been consummated and the forward sale agreement had been fully physically settled on January 1, 2023.

The unaudited pro forma condensed combined statement of income for the six months ended June 30, 2024, combines the unaudited consolidated statement of income of Atlantic Union for the six months ended June 30, 2024, with the unaudited consolidated statement of income of American National for the three months ended March 31, 2024, as well as the unaudited consolidated statement of income of Sandy Spring for the six months ended June 30, 2024, giving effect to the American National acquisition, the Merger and the forward sale agreement as if the American National acquisition and the Merger had been consummated and the forward sale agreement had been fully physically settled on January 1, 2023.

The unaudited pro forma condensed combined financial data was derived from, and should be read in conjunction with, the following historical financial statements and the accompanying notes, which are included or incorporated by reference into this prospectus supplement and the accompanying base prospectus:

The unaudited pro forma condensed combined financial data should also be read together with other financial data included elsewhere or incorporated by reference into this prospectus supplement, including the unaudited pro forma condensed combined financial statements of Atlantic Union and American National as of and for the year ended December 31, 2023, attached as Exhibit 99.2 to Atlantic Union’s Amended Current Report on Form 8-K/A dated April 18, 2024.

The foregoing historical financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”). The unaudited pro forma condensed combined financial data has been prepared based on the aforementioned historical financial statements and the assumptions and adjustments as described in the notes to the unaudited pro forma condensed combined financial data. The pro forma adjustments reflect transaction accounting adjustments related to the American National acquisition, the Merger and the forward sale agreement, all of which are discussed in further detail below. Amounts presented reflect the accounting for the acquisitions of American National and Sandy Spring by Atlantic Union. The unaudited pro forma condensed combined financial data is presented for illustrative purposes only and does not purport to represent the combined company’s consolidated results of operations or consolidated financial position that would actually have occurred had the American National acquisition and the Merger been consummated and the forward sale agreement been fully physically settled on the dates assumed or to project the combined company’s consolidated results of operations or consolidated financial position for any future date or period.

The unaudited pro forma condensed combined financial data appearing below also does not consider any potential effects of changes in market conditions, certain asset dispositions (including the proposed sale of approximately $2 billion of commercial real estate loans at, or shortly after, the completion of the Merger), cost savings, or revenue synergies, among other factors, and, accordingly, does not attempt to predict or suggest future results. In addition, as explained in more detail in the accompanying notes, the preliminary allocation of the pro forma purchase price reflected in the unaudited pro forma condensed combined financial data is subject to adjustment and may vary significantly from the actual purchase price allocation that will be recorded upon completion of the Merger.

The American National acquisition

On April 1, 2024, Atlantic Union completed its previously announced merger with American National, pursuant to the Agreement and Plan of Merger, dated as of July 24, 2023, by and between Atlantic Union and American National. At the effective time of the merger, American National merged with and into Atlantic Union, with Atlantic Union continuing as the surviving corporation. Immediately following the merger, American National Bank and Trust Company, American National’s wholly owned subsidiary bank, merged with and into Atlantic Union Bank, with Atlantic Union Bank continuing as the surviving bank. American National’s results of operations have been included in Atlantic Union’s consolidated results since the date of the American National acquisition.

The unaudited pro forma condensed combined financial information has been prepared using the acquisition method of accounting for business combinations under U.S. GAAP, with Atlantic Union as the acquirer for accounting purposes. Certain reclassifications have been made to the historical financial statements of American National to conform to the presentation in Atlantic Union’s financial statements. The unaudited pro forma condensed combined balance sheet as of June 30, 2024, does not reflect transaction accounting adjustments related to the American National acquisition as the American National acquisition is already reflected in the historical balance sheet of Atlantic Union as of June 30, 2024. The unaudited pro forma condensed combined statements of income for the six months ended June 30, 2024, and for the year ended December 31, 2023, are presented as if the American National acquisition occurred on January 1, 2023, each of which does not necessarily indicate the results of operations if the businesses had been combined for the historical period, or the results of operations in future periods.

Accounting for the Sandy Spring Merger

The acquisition of Sandy Spring will be accounted for using the purchase method of accounting. The total purchase price will be allocated to the tangible and intangible assets and liabilities acquired based on their respective fair values. The allocation of the purchase price reflected in the following unaudited pro forma condensed combined financial data is preliminary and is subject to adjustment upon receipt of, among other things, appraisals of some of the assets and liabilities of Sandy Spring. Upon completion of the Merger, a final determination of the fair values of Sandy Spring assets acquired and liabilities assumed will be performed. Any changes in the fair values of the net assets or total purchase price as compared with the information shown in the unaudited pro forma condensed combined financial data may change the amount of the total purchase consideration allocated to goodwill, deferred taxes, and other assets and liabilities, and may impact the combined company’s statement of income.

Forward sale agreement

In connection with the forward sale agreement, the forward purchaser or its affiliate is expected to borrow from third parties an aggregate of shares of our common stock. Such borrowed shares of our common stock will be delivered by the forward seller for sale to the underwriters in this offering. In the event that (i) the forward purchaser (or its affiliate) is unable through commercially reasonable efforts to borrow and deliver for sale to the underwriters on the anticipated closing date the number of shares of our common stock to be sold to the underwriters or (ii) in the forward purchaser’s commercially reasonable judgment either it is impracticable to do so or the forward purchaser (or its affiliate) would incur a stock loan rate greater than a specified rate to borrow and deliver for sale to the underwriters on the anticipated closing date such number of shares of our common stock, or if certain other conditions to the forward seller’s obligations have not been satisfied, then we will issue and sell directly to the underwriters a number of shares of our common stock equal to the number of shares of our common stock that the forward purchaser or its affiliate does not borrow and deliver. Under such circumstances, the number of shares of our common stock underlying the forward sale agreement will be decreased by the number of shares of our common stock that we issue and sell to the underwriters. For purposes of this section “Unaudited Pro Forma Condensed Combined Financial Data,” we have assumed a total offering size of $350.0 million in the offering contemplated by this prospectus supplement.

We will not initially receive any proceeds from the sale of the shares of our common stock sold by the forward seller to the underwriter. We expect to physically settle the forward sale agreement at the assumed offering size of $350.0 million (by the delivery of shares of our common stock) and receive proceeds from the sale of those shares of our common stock upon one or more forward settlement dates within approximately 18 months from the date hereof. We may also elect cash settlement or net share settlement for all or a portion of our obligations under the forward sale agreement. If we elect to cash settle or net share settle the forward sale agreement, then we may not receive any proceeds from the issuance of shares of our common stock in respect of the forward sale agreement, and we will instead receive or pay cash (in the case of cash settlement) or receive or deliver shares of our common stock (in the case of net share settlement).

Basis of Pro Forma Presentation

The historical financial data of Atlantic Union, American National and Sandy Spring has been adjusted to give pro forma effect to the transaction accounting required for the American National acquisition, the Merger and the forward sale agreement. The adjustments in the unaudited pro forma condensed combined financial data have been identified and presented to provide relevant information necessary to evaluate the financial overview of the combined company upon closing of the Merger and full physical settlement of the forward sale agreement at the assumed offering size of $350.0 million.

The unaudited pro forma condensed combined financial data is not necessarily indicative of what the combined company’s balance sheet or statement of income would have been had the American National acquisition been completed, the Merger been completed and the forward sale agreement been fully physically settled at the assumed offering size of $350.0 million as of the dates indicated, nor do they purport to project the future financial position or operating results of the combined company. The unaudited pro forma condensed combined financial data is presented for illustrative purposes only and does not reflect the costs of any integration activities or cost savings or synergies that may be achieved because of the Merger. American National and Atlantic Union did not have any historical material relationship before the American National acquisition. Sandy Spring and Atlantic Union have not had any historical material relationship before the Merger. Accordingly, no pro forma adjustments were required to eliminate activities among the companies.

Unaudited Pro Forma Condensed Combined Balance Sheet

(Dollars in thousands, except share and per share data)

Please refer to the notes to the unaudited pro forma condensed combined financial data.

Unaudited Pro Forma Condensed Combined Statement of Income

(Dollars in thousands, except share and per share data)

Please refer to the notes to the unaudited pro forma condensed combined financial data.

Unaudited Pro Forma Condensed Combined Statement of Income

(Dollars in thousands, except share and per share data)

Please refer to the notes to the unaudited pro forma condensed combined financial data.

NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

Note 1 — Basis of Presentation

The pro forma adjustments have been prepared, in the case of the unaudited pro forma condensed combined balance sheet as of June 30, 2024, as if the Merger had been consummated and the forward sale agreement had been fully physically settled at the assumed offering size of $350.0 million on June 30, 2024, in the case of the unaudited pro forma condensed combined statement of income for the year ended December 31, 2023, as if the American National acquisition had been consummated, the Merger had been consummated and the forward sale agreement had been fully physically settled at the assumed offering size of $350.0 million on January 1, 2023, and in the case of the unaudited pro forma condensed combined statement of income for the six months ended June 30, 2024, as if the American National acquisition had been consummated, the Merger had been consummated and the forward sale agreement had been fully physically settled at the assumed offering size of $350.0 million on January 1, 2023.

The unaudited pro forma condensed combined financial data has been prepared assuming the purchase method of accounting in accordance with GAAP. Under this method, Sandy Spring’s assets and liabilities as of the date of the Merger and American National’s assets and liabilities as of April 1, 2024 will be recorded at their respective fair values and added to those of Atlantic Union. Any difference between the purchase price for Sandy Spring and the fair value of the identifiable net assets acquired (including intangibles) will be recorded as goodwill. Similarly, the excess of the merger consideration over the fair value of American National’s net assets will be allocated to goodwill. The goodwill resulting from the acquisition will not be amortized to expense, but instead will be reviewed for impairment at least annually. The pro formas are based on preliminary accounting conclusions and are subject to potential revisions with further analysis.

The pro forma adjustments represent management’s estimates based on information available as of the date of this prospectus supplement and are subject to change as additional information becomes available and additional analyses are performed. Atlantic Union management considers this basis of presentation to be reasonable under the circumstances.

One-time direct and incremental transaction costs anticipated to be incurred prior to, or concurrent with, the closing of the Merger will be expensed as incurred under ASC 805 and are assumed to be cash settled.

Atlantic Union has performed a preliminary review of Sandy Spring’s and Atlantic Union’s accounting policies, and no material impacts are expected to be required as a result of the review performed.

Note 2 — Adjustments to the Unaudited Pro Forma Condensed Combined Balance Sheet

The following pro forma adjustments have been reflected in the unaudited pro forma condensed combined balance sheet. All adjustments are preliminary and are based on current valuations, estimates, and assumptions, which are subject to change. Subsequent to the completion of the Merger, Atlantic Union will engage an independent third-party valuation firm to determine the fair value of the assets acquired and liabilities assumed, which could significantly change the amount of the estimated fair values used in the pro forma financial information presented.

Note 3 – Adjustments to the Unaudited Pro Forma Condensed Combined Statements of Income

The following pro forma adjustments have been reflected in the unaudited pro forma condensed combined statements of income. All adjustments are preliminary and are based on current valuations, estimates, and assumptions, which are subject to change.

Note 4 – Preliminary Pro Forma Allocation of Purchase Price

The preliminary pro forma allocation of the purchase price reflected in the pro forma condensed combined financial information is subject to adjustment and may vary from the actual purchase price allocation that will be recorded at the time the Merger is completed. Adjustments may include, but not be limited to, changes in (a) Sandy Spring’s balance sheet and operating results through the effective time of the Merger; (b) the aggregate value of merger consideration paid if the price of shares of Atlantic Union common stock varies from the assumed $37.88 per share; (c) total merger-related costs if consummation and/or implementation costs vary from currently estimated amounts; and (d) the underlying values of assets and liabilities if market and credit conditions differ from current assumptions.

The pro forma adjustments include the estimated purchase accounting entries to record the Merger transaction. The excess of the purchase price over the fair value of net assets acquired, net of deferred taxes, is allocated to goodwill. Estimated fair value adjustments included in the pro forma condensed combined financial information are based upon available information and certain assumptions considered reasonable as of the date of this prospectus supplement, and may be revised as additional information becomes available.

The following table shows the preliminary pro forma allocation of the estimated consideration to be paid in the Merger for Sandy Spring common stock, based on the closing share price of Atlantic Union common stock of $37.88 on the NYSE on October 11, 2024 to the acquired identifiable assets and liabilities assumed and the pro forma goodwill generated from the Merger:

The purchase price is contingent on the price per share of Atlantic Union common stock at the effective time of the Merger, which has not yet occurred. The following table summarizes the sensitivity of the purchase price with a sensitivity analysis assuming a 10% increase and a 10% decrease in the price per share of Atlantic Union common stock from $37.88, the closing share price of Atlantic Union common stock on the NYSE on October 11, 2024, and its impact on the preliminary goodwill estimate.

Note 5 – Estimated Amortization/Accretion of Acquisition Accounting Adjustments

The following table sets forth an estimate of the expected effects of the estimated aggregate acquisition accounting adjustments reflected in the pro forma combined condensed financial statements on the future pre-tax net income of Sandy Spring after the Merger.

The actual effect of purchase accounting adjustments on the future pre-tax income of Sandy Spring will differ from these estimates based on the closing date estimates of fair values and, if applicable, the use of different amortization methods than assumed above. Refer to Notes 2 and 3 above for additional information on assumed amortization methods.

Note 6 – Earnings per Share Information

The pro forma weighted average shares calculations have been performed for the year ended December 31, 2023 and six months ended June 30, 2024 using the historical weighted average shares outstanding, and the issuance of additional shares in connection with the Merger and the forward sale agreement, assuming they occurred, and the forward sale agreement was fully physically settled at the assumed offering size of $350.0 million. As the Merger and the forward sale agreement are being reflected as if they had occurred, and the forward sale agreement was fully physically settled at the assumed offering size of $350.0 million, at the beginning of the period presented, the calculation of weighted average shares outstanding for both basic and diluted earnings per share assumes that the shares issuable relating to the Merger and the forward sale agreement have been outstanding for the entire periods presented.

The above basic and diluted calculations include the following potential common stock as of December 31, 2023 and June 30, 2024 in the computations of earnings per share attributable to common shareholders of the combined company for the periods indicated: