Sec Form 4 Filing - DEL VALLE PEROCHENA ANTONIO @ BYLINE BANCORP, INC. - 2024-02-29

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person DEL VALLE PEROCHENA ANTONIO 2. Issuer Name and Ticker or Trading Symbol BYLINE BANCORP, INC. [ BY] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 180 NORTH LASALLE STREET, SUITE 300 3. Date of Earliest Transaction (MM/DD/YY) 02/29/2024 (Street) CHICAGO, IL60601 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common stock 02/29/2024 P 2,897 A $ 20.7558 11,828,042 I ( 1 ) By MBG Investors I, L.P. Common stock 03/01/2024 P 7,103 A $ 20.6457 11,835,145 I ( 1 ) By MBG Investors I, L.P.

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other DEL VALLE PEROCHENA ANTONIO 180 NORTH LASALLE STREET SUITE 300 CHICAGO, IL60601 X X Signatures /s/ Ana Casanueva, Attorney-in-fact for Antonio del Valle Perochena 03/04/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Mr. Antonio del Valle Perochena is the general partner of MBG Investors I, L.P. and possesses sole voting and investment power with respect to the shares of common stock held by MBG Investors I, L.P. Mr. del Valle Perochena owns 16.68% of the partnership interests of MBG Investors I, L.P. Mr. del Valle Perochena disclaims beneficial ownership of such shares of common stock except to the extent of his pecuniary interest therein, and this report shall not be deemed an admission that he is the beneficial owner of such disclaimed shares of common stock for purposes of Section 16 or for any other purpose. The address for MBG Investors I, L.P. is 365 Bay Street, Suite 800, M5H2V1 Toronto, Ontario, Canada

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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