BUSE

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 27, 2026

First Busey Corporation (Exact name of Registrant as specified in its charter)

Nevada0-1595037-1078406 (State of Incorporation)(Commission File Number)(I.R.S. Employer Identification No.)

11440 Tomahawk Creek Parkway Leawood, Kansas 66211

(Address of Principal Executive Offices)

(217) 365-4544

(Registrant’s telephone number, including area code) N/A (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:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each classTrading Symbol(s)Name of each exchange on which registered Common Stock, $0.001 par valueBUSENasdaq Stock Market LLC Depositary Shares, each representing a 1/40th interest in a share of 8.25% Fixed-Rate Series B Non-Cumulative Perpetual Preferred Stock, $0.001 par value BUSEPNasdaq Stock Market LLC

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). ☐ 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. ☐

Item 2.02    Results of Operations and Financial Condition. On January 27, 2026, First Busey Corporation (“Busey”) issued a press release (“Earnings Release”) disclosing financial results for the quarter ended December 31, 2025. A copy of the Earnings Release is attached hereto as Exhibit 99.1 and is incorporated herein by reference. The information in Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto is being “furnished” and will not, except to the extent required by applicable law or regulation, be deemed “filed” by Busey for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (“Exchange Act”), or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended (“Securities Act”), or the Exchange Act.

Item 5.02    Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. Departure of Michael J. Maddox On January 27, 2026, Busey and Busey Bank (the “Bank”) entered into a letter agreement (the “Separation Letter”) with Michael J. Maddox, the former President and Vice Chairman of Busey and President and Chief Executive Officer of the Bank, confirming the separation of Mr. Maddox from his employment with Busey and its subsidiaries and resignation from Busey’s and the Bank’s Board of Directors, each effective January 27, 2026. Under the terms of the Separation Letter, subject to the effectiveness of a release of claims, Mr. Maddox will receive (a) cash severance in the amount of $4,363,333, representing the base salary and annual bonuses he would have earned through the third anniversary of Busey’s acquisition of CrossFirst Bankshares, Inc. (“CrossFirst”), (b) his annual bonus for 2025, determined based on actual performance for the 2025 performance year, (c) a cash amount of $4,175,559, representing the unvested portion of his retention award granted pursuant to the letter agreement he entered into with Busey on August 26, 2024 in connection with Busey’s acquisition of CrossFirst, and (d) reimbursement of reasonable outplacement expenses, subject to a cap of $25,000. Mr. Maddox’s outstanding unvested equity awards will vest in full, with any performance-based vesting conditions deemed satisfied at target. In addition, Mr. Maddox continues to be bound by his post-employment non-competition, non-solicitation, and non-disclo

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 28, 2025

First Busey Corporation (Exact name of Registrant as specified in its charter)

Nevada0-1595037-1078406 (State of Incorporation)(Commission File Number)(I.R.S. Employer Identification No.)

11440 Tomahawk Creek Parkway Leawood, Kansas 66211

(Address of Principal Executive Offices)

(217) 365-4544

(Registrant’s telephone number, including area code) N/A (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:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each classTrading Symbol(s)Name of each exchange on which registered Common Stock, $0.001 par valueBUSENasdaq Stock Market LLC Depositary Shares, each representing a 1/40th interest in a share of 8.25% Fixed-Rate Series B Non-Cumulative Perpetual Preferred Stock, $0.001 par value BUSEPNasdaq Stock Market LLC

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). ☐ 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. ☐

Item 2.02    Results of Operations and Financial Condition. On October 28, 2025, First Busey Corporation (“Busey”) issued a press release (“Earnings Release”) disclosing financial results for the quarter ended September 30, 2025. A copy of the Earnings Release is attached hereto as Exhibit 99.1 and is incorporated herein by reference. The information in Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto is being “furnished” and will not, except to the extent required by applicable law or regulation, be deemed “filed” by Busey for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (“Exchange Act”), or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended (“Securities Act”), or the Exchange Act.

Item 7.01    Regulation FD Disclosure. On October 28, 2025, Busey published its Earnings Investor Presentation discussing financial results for the quarter ended September 30, 2025. A copy is attached hereto as Exhibit 99.2 and is incorporated herein by reference. The information in Item 7.01 of this Current Report on Form 8-K and Exhibit 99.2 attached hereto is being “furnished” and will not, except to the extent required by applicable law or regulation, be deemed “filed” by Busey for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act or the Exchange Act.

Item 9.01.    Financial Statements and Exhibits.

Exhibit Number Description of Exhibit 99.1Earnings Release issued by First Busey Corporation, dated October 28, 2025

99.2Earnings Investor Presentation issued by First Busey Corporation, dated October 28, 2025

104Cover Page Interactive Data File (embedded within the Inline XBRL document and included in Exhibit 101)

2

Signature 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, thereunto duly authorized.

FIRST BUSEY CORPORATION

Date:October 28, 2025 By:/s/ CHRISTOPHER H.M. CHAN Christopher H.M. Chan Chief Financial Officer, Executive Vice President

3

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 22, 2025

First Busey Corporation (Exact name of Registrant as specified in its charter)

Nevada0-1595037-1078406 (State of Incorporation)(Commission File Number)(I.R.S. Employer Identification No.)

11440 Tomahawk Creek Parkway Leawood, Kansas 66211

(Address of Principal Executive Offices)

(217) 365-4544

(Registrant’s telephone number, including area code) N/A (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:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each classTrading Symbol(s)Name of each exchange on which registered Common Stock, $0.001 par valueBUSENasdaq Stock Market LLC Depositary Shares, each representing a 1/40th interest in a share of 8.25% Fixed-Rate Series B Non-Cumulative Perpetual Preferred Stock, $0.001 par value BUSEPNasdaq Stock Market LLC

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). ☐ 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. ☐

Item 2.02    Results of Operations and Financial Condition. On July 22, 2025, First Busey Corporation (“Busey”) issued a press release (“Earnings Release”) disclosing financial results for the quarter ended June 30, 2025. A copy of the Earnings Release is attached hereto as Exhibit 99.1 and is incorporated herein by reference. The information in Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto is being “furnished” and will not, except to the extent required by applicable law or regulation, be deemed “filed” by Busey for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (“Exchange Act”), or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended (“Securities Act”), or the Exchange Act.

Item 7.01    Regulation FD Disclosure. On July 22, 2025, Busey published its Earnings Investor Presentation discussing financial results for the quarter ended June 30, 2025. A copy is attached hereto as Exhibit 99.2 and is incorporated herein by reference. The information in Item 7.01 of this Current Report on Form 8-K and Exhibit 99.2 attached hereto is being “furnished” and will not, except to the extent required by applicable law or regulation, be deemed “filed” by Busey for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act or the Exchange Act.

Item 8.01    Other Events. Franchise Tax Matter As previously disclosed, in 2021, Busey received an inquiry from the Illinois Secretary of State (the “ISOS”), pursuant to which the ISOS asked for additional information regarding certain of Busey’s franchise tax filings and the calculation of amounts due thereunder. The franchise tax is established by the Illinois Business Corporation Act (“BCA”) 805 ILCS 5/1 et seq., and is a tax imposed on foreign and domestic corporations for the privilege of conducting business in Illinois. Busey has been cooperating with the inquiry since the initial outreach from the ISOS in 2021 and in October 2024 delivered additional BCA forms requested by the ISOS, with a full reservation of rights by Busey. On March 20, 2025, the ISOS requested that Busey resubmit the requested forms using a proposed methodology for paid-in capital that First Busey views as inconsistent with th