United Community Banks : Investor Presentation Third Quarter 2021

3Q21 Investor Presentation

October 19, 2021

Important Information For Shareholders and Investors

This presentation contains information related to a proposed merger of United Community Banks, Inc. ("United") with Reliant Bancorp, Inc. ("Reliant"). In connection with the proposed merger, United has filed with the Securities and Exchange Commission ("SEC") a registration statement on Form S-4 that includes the proxy statement of Reliant to be sent to Reliant's shareholders seeking their approval of the merger. The registration statement also contains a prospectus of United to register the shares of United common stock to be issued in connection with the mergers. A definitive proxy statement/prospectus will also be provided to Reliant's shareholders as required by applicable law. INVESTORS AND SHAREHOLDERS OF RELIANT ARE ENCOURAGED TO READ THE APPLICABLE REGISTRATION STATEMENT, INCLUDING THE DEFINITIVE PROXY STATEMENT/PROSPECTUS THAT WILL BE A PART OF THE REGISTRATION STATEMENT WHEN IT BECOMES AVAILABLE AND ANY OTHER RELEVANT DOCUMENTS FILED BY UNITED WITH THE SEC, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THE REGISTRATION STATEMENT AND THOSE OTHER DOCUMENTS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT UNITED, RELIANT AND THE PROPOSED TRANSACTION.

The registration statement and other documents filed with the SEC may be obtained for free at the SEC's website (www.sec.gov). You will also be able to obtain these documents, free of charge, from United at the "Investor Relations" section of United's website at www.UCBI.comor from Reliant at the "Investors" section of Reliant's website at www.reliantbank.com. Copies of the definitive proxy statement/prospectus will also be made available, free of charge, by contacting United Community Banks, Inc., P.O. Box 398, Blairsville, GA 30514, Attn: Jefferson Harralson, Telephone: [phone], Reliant Bancorp, Inc., 1736 Carothers Parkway Suite 100, Brentwood, TN 37027, Attn: Jerry Cooksey, Telephone: [phone].

This communication does not constitute an offer to sell, the solicitation of an offer to sell or the solicitation of an offer to buy securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of such jurisdiction. This communication is also not a solicitation of any vote or approval with respect to the proposed transaction or otherwise.

PARTICIPANTS IN THE TRANSACTIONS

United, Reliant and certain of their respective directors and executive officers, under the rules of the SEC, may be deemed to be participants in the solicitation of proxies from Reliant's shareholders in favor of the approval of the merger. Information about the directors and officers of United and their ownership of United common stock can also be found in United's definitive proxy statement in connection with its 2021 annual meeting of shareholders, as filed with the SEC on March 30, 2021, and other documents subsequently filed by United with the SEC. Information about the directors and executive officers of Reliant and their ownership of Reliant capital stock, as well as information regarding the interests of other persons who may be deemed participants in the transaction, may be found in Reliant's definitive proxy statement in connection with its 2021 annual meeting of shareholders, as filed with the SEC on April 8, 2021, and other documents subsequently filed by Reliant with the SEC. Free copies of these documents may be obtained as described above.

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Disclosures

CAUTIONARY STATEMENT

This communication contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. In general, forward-looking statements usually may be identified through use of words such as "may," "believe," "expect," "anticipate," "intend," "will," "should," "plan," "estimate," "predict," "continue" and "potential" or the negative of these terms or other comparable terminology, and include statements related to the expected timing of the closing of the merger with Reliant (the "merger"), the expected returns and other benefits of the merger to shareholders, expected improvement in operating efficiency resulting from the merger, estimated expense reductions resulting from the transaction and the timing of achievement of such reductions, the impact on and timing of the recovery of the impact on tangible book value, and the effect of the merger on United's capital ratios. Forward-looking statements are not historical facts and represent management's beliefs, based upon information available at the time the statements are made, with regard to the matters addressed; they are not guarantees of future performance. Actual results may prove to be materially different from the results expressed or implied by the forward-looking statements. Forward-looking statements are subject to numerous assumptions, risks and uncertainties that change over time and could cause actual results or financial condition to differ materially from those expressed in or implied by such statements.

Factors that could cause or contribute to such differences include, but are not limited to (1) the risk that the cost savings from the merger may not be realized or take longer than anticipated to be realized, (2) disruption from the merger with customer, supplier, employee or other business partner relationships, (3) the occurrence of any event, change or other circumstances that could give rise to the termination of the merger agreement, (4) the failure to obtain the necessary approval by the shareholders of Reliant, (5) the possibility that the costs, fees, expenses and charges related to the merger may be greater than anticipated, (6) the ability by United to obtain required governmental approvals of the merger, (7) reputational risk and the reaction of the companies' customers, suppliers, employees or other business partners to the merger, (8) the failure of the closing conditions in the merger agreement with Reliant to be satisfied, or any unexpected delay in closing the merger, (9) the risks relating to the integration of either Aquesta Financial Holdings, Inc.'s or Reliant's operations into the operations of United, including the risk that such integration will be materially delayed or will be more costly or difficult than expected, (10) the risk of potential litigation or regulatory action related to mergers, (11) the risks associated with United's pursuit of future acquisitions, (12) the risk of expansion into new geographic or product markets, (13) the dilution caused by United's issuance of additional shares of its common stock in mergers, and (14) general competitive, economic, political and market conditions. Further information regarding additional factors which could affect the forward-looking statements can be found in the cautionary language included under the headings "Cautionary Note Regarding Forward-Looking Statements" and "Risk Factors" in United's Annual Report on Form 10-K for the year ended December 31, 2020, and other documents subsequently filed by United with the SEC.

Many of these factors are beyond United's and Reliant's ability to control or predict. If one or more events related to these or other risks or uncertainties materialize, or if the underlying assumptions prove to be incorrect, actual results may differ materially from the forward-looking statements. Accordingly, shareholders and investors should not place undue reliance on any such forward-looking statements. Any forward-looking statement speaks only as of the date of this communication, and United undertakes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. New risks and uncertainties may emerge from time to time, and it is not possible for United to predict their occurrence or how they will affect United or Reliant.

United qualifies all forward-looking statements by these cautionary statements.

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Disclosures

NON-GAAP MEASURES

This Investor Presentation includes financial information determined by methods other than in accordance with generally accepted accounting principles ("GAAP"). This financial information includes certain operating performance measures, which exclude merger-related and other charges that are not considered part of recurring operations. Such measures include: "Earnings per share - operating," "Diluted earnings per share - operating," "Tangible book value per share," "Return on common equity - operating," "Return on tangible common equity - operating," "Return on assets - operating," "Return on assets - pre-taxpre-provision, excluding merger-related and other charges," "Efficiency ratio - operating," "Expenses - operating," and "Tangible common equity to tangible assets."

Management has included these non-GAAP measures because it believes these measures may provide useful supplemental information for evaluating United's underlying performance trends. Further, management uses these measures in managing and evaluating United's business and intends to refer to them in discussions about our operations and performance. Operating performance measures should be viewed in addition to, and not as an alternative to or substitute for, measures determined in accordance with GAAP, and are not necessarily comparable to non-GAAP measures that may be presented by other companies. To the extent applicable, reconciliations of these non-GAAP measures to the most directly comparable GAAP measures can be found in the 'Non-GAAP Reconciliation Tables' included in the exhibits to this Presentation.

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United Community Banks, Inc.

Committed to Service Since 1950

Company Overview

Regional Full Service Branch Network

National Navitas and SBA Markets

Banking Offices

Premier Southeast Regional Bank

• Metro-focusedbranch network with locations in the fastest growing MSAs in the Southeast
• 162 branches, 9 LPOs, and 4 mortgage loan offices across six Southeast states
• Top 10 market share in GA, SC and TN*
• Proven ability to integrate - 11 transactions completed over the past 10 years
• Closed the Aquesta acquisition October 1, adding $754 million in total assets with locations in Charlotte and Wilmington

Extended Navitas and SBA Markets

• Offered in 48 states across the continental U.S.
• SBA business has both in-footprint and national business (4 specific verticals)
• Navitas subsidiary is a technology enabled small-ticket,essential-use commercial equipment finance provider

Note: See glossary located at the end of this presentation for reference on certain acronyms *Pro forma for Reliant close expected in 1Q22

$19.5

BILLION IN

TOTAL ASSETS

$4.5

BILLION IN AUA

13.4%

TIER 1 RBC

$0.20

QUARTERLY DIVIDEND -

UP 11% YOY

171

BANKING OFFICES

ACROSS THE

SOUTHEAST

#1 IN CUSTOMER

SATISFACTION

in 2021 with Retail Banking

in the Southeast - J.D.

Power

$11.2

BILLION IN

TOTAL LOANS

$16.9

BILLION IN

TOTAL DEPOSITS

100 BEST BANKS IN

AMERICA

in 2021 for the eighth

consecutive year - Forbes

#2 Highest Net Promoter Score

among all banks nationwide

• J.D. Power

2020 TOP

WORKPLACES

in S.C. & Atlanta - Greenville

Business Magazine & Atlanta

Journal Constitution

BEST BANKS TO

WORK FOR

in 2020 for the fourth consecutive year - American Banker 5