X0202 SCHEDULE 13G/A 0001104659-25-013012 0001710094 XXXXXXXX LIVE 4 Common Stock, par value $0.01 per share 08/07/2026 0001702750 BYLINE BANCORP, INC 124411109 180 NORTH LASALLE STREET SUITE 300 CHICAGO IL 60601 Rule 13d-1(d) MBG INVESTORS I, LP A6 11535145.00 11535145.00 11535145.00 25.5 PN ANTONIO DEL VALLE PEROCHENA O5 40808.00 11535145.00 40808.00 11535145.00 11575953.00 25.6 HC IN BYLINE BANCORP, INC 180 NORTH LASALLE STREET, SUITE 300, CHICAGO, IL, 60601. MBG Investors I, L.P., a Canadian limited partnership ("MBG") and Antonio del Valle Perochena, a Mexican citizen (together with MBG, the "Reporting Persons"). 365 Bay Street, Suite 800, M5H2V1 Toronto, Ontario, Canada. The place of organization of MBG is Toronto, Ontario, Canada. The citizenship of Antonio del Valle Perochena is Mexican. Y See row 9 on each cover page above. See row 11 on each cover page above. See row 5 on each cover page above. See row 6 on each of cover page above. See row 7 on each cover page above. See row 8 on each cover page above. This Schedule 13G/A is being filed to reflect the reduction in MBG's beneficial ownership as a result of the sale to and repurchase by the Issuer of 300,000 shares of Common Stock (the "Shares") pursuant to a Stock Repurchase Agreement (the "Stock Repurchase Agreement") dated as of August 7, 2026 between MBG and the Issuer. Under the Stock Repurchase Agreement, the Issuer agreed to purchase the Shares at a price of $39.10 per Share, which price was determined based on the five (5) day average closing price for the Common Stock on the NYSE for the period from July 27, 2026 through July 31, 2026, for an aggregate purchase price of $11.73 million. Percent of class calculations are based on 45,186,420 shares of Common Stock outstanding as of August 3, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed on August 6, 2026. Y Y Y Y Y Exhibit A Joint Filing Agreement MBG INVESTORS I, LP /s/ Antonio del Valle Perochena 08/14/2026 ANTONIO DEL VALLE PEROCHENA /s/ Antonio del Valle Perochena 08/14/2026