BYLINE BANCORP INC

Report of Independent Registered Public Accounting Firm

To the Stockholders and the Board of Directors of

Byline Bancorp, Inc. and Subsidiaries

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated statements of financial condition of Byline Bancorp, Inc. and Subsidiaries (the “Company”) as of December 31, 2023 and 2022, the related consolidated statements of operations, comprehensive income (loss), changes in stockholders’ equity, and cash flows for each of the three years in the period ended December 31, 2023, and the related notes (collectively referred to as the consolidated financial statements). We also have audited the Company’s internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, theconsolidated financial position of the Company as of December 31, 2023 and 2022, and the consolidated results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control – Integrated Framework (2013) issued by COSO.

Change in Accounting Principle

The Company changed its method of accounting for credit losses effective January 1, 2022, due to the adoption of Accounting Standards Codification Topic 326: Financial Instruments – Credit Losses (“Topic 326”). The Company adopted the new credit loss standard using the modified retrospective approach such that prior period amounts are not adjusted and continue to be reported in accordance with previously applicable generally accepted accounting principles.

Basis for Opinions

The Company’s management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company’s consolidated financial statements and an opinion on the Company’s internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (“PCAOB”) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the consolidated financial statements included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures to respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of theconsolidated financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matter

The critical audit matters communicated below are matters arising from the current period audit of the consolidated financial statements that were communicated or required to be communicated to the audit committee and that (1) relate to accounts or disclosures that are material to the consolidated financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matters below, providing a separate opinion on the critical audit matters or on the accounts or disclosures to which it relates.

Allowance for Credit Losses for Loans and Leases – Identifying Loans to be Individually Evaluated, Loan Risk Ratings, Reasonable and Supportable Forecasts and Qualitative Factors

As described in Note 5 to the consolidated financial statements, the Company’s allowance for credit losses for loans and leases was $101.7 million as of December 31, 2023, and consists of both a historical credit loss experience component and management’s estimates of current conditions and reasonable and supportable forecasts. The Company’s allowance for credit losses for loans and leases is a valuation account that is deducted from the amortized cost basis of loans and leases to present the net carrying value expected to be collected on such loans and leases and is a material and complex estimate requiring significant management judgment in the estimation of expected lifetime losses within the loan and lease portfolio as of the balance sheet date.

We identified management’s risk rating of loans, identification of loans to be individually evaluated, the reasonable and supportable forecasts, and the estimate of qualitative risk factor adjustments that are intended to capture internal and external trends not reflected in historical loss history, and the selection of the methodology and economic variables and forecast scenarios utilized, as a critical audit matter. In estimating the allowance for credit losses on loans and leases, the Company utilizes relevant information from internal and external sources relating to past events, current conditions, and reasonable and supportable forecasts. The Company considers loan-specific risk characteristics for each loan and lease segment, identifies loans to be individually evaluated, and estimates losses for each loan and lease segment based upon their nature, historical experience, and risk profile. This process requires significant management judgment in the review of the loan and lease portfolio and identification of individually evaluated loans based upon the characteristics of loans and leases. In addition, estimation of the lifetime expected credit losses for loans and leases requires significant management judgment, particularly as it relates to forward-looking information through the use of qualitative risk factors and peer data applied over the forecasted life of the loans and leases. Auditing these complex judgments and assumptions involved especially challenging auditor judgment due to the nature and extent of audit evidence and effort required to address these matters.

The primary procedures we performed to address this critical audit matter included:

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Testing the design, implementation and operating effectiveness of controls relating to management’s calculation of the allowance for credit losses for loans and leases, including controls over the review of loans and leases and identification of individually evaluated loans, evaluation of the qualitative and forecast factors, model development and validation, and selection and application of accounting policies, and disclosures.

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Evaluating the appropriateness of the Company’s models, assumptions and elections involved, the economic variables selected based on the correlation to historical charge-offs, and the forecasting assumptions used in the reasonable and supportable forecast adjustment.

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Evaluating the appropriateness of the Company’s loan and lease risk rating policy and testing a risk-based targeted selection of loans and leases to gain substantive evidence that the Company is appropriately classifying loans and leases by risk category, and identifying loans and leases to be individually evaluated in accordance with its policies, and that the allowance for credit losses on those loans and leases is reasonable.

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Evaluating the reasonableness and appropriateness of the estimated qualitative risk factor adjustments utilized by management in forming the loss estimate by comparing the qualitative adjustments to relevant external data, including historical trends.

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Testing the mathematical accuracy and computation of the allowance for credit losses for loans and leases by reperforming or independently calculating significant elements of the allowance, including quantitative historical loss factors applied to the loan and lease segments based on risk ratings and utilizing relevant source documents, including the completeness and accuracy of the data used in the calculation. Additionally, testing the accuracy of the impact of forecasting assumptions used in the reasonable and supportable forecast adjustment.

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Evaluating the accuracy and completeness of the Company’s disclosures in accordance with Accounting Standards Codification Topic 326, Financial Instruments – Credit Losses.

Business Combination – Inland Bancorp, Inc. acquired loans and core deposit intangible valuation

As discussed in Note 1 and Note 3 to the consolidated financial statements, on July 1, 2023, the Company completed the acquisition of Inland Bancorp, Inc. (Inland). Total merger consideration, including cash and stock transactions, was $138.9 million. The fair value of total assets acquired as a result of the merger totaled $1.2 billion, with the fair value of loans totaling $808.0 million before an allowance for credit losses adjustment of $10.6 million related to purchased credit deteriorated loans. The overall transaction resulted in the recognition of $33.4 million of goodwill. The merger was accounted for using the acquisition method of accounting in which assets, liabilities, and consideration exchanged were recorded at their respective fair values at the merger date. To estimate the fair value of the acquired loans, the Company utilized a discounted cash flow methodology that involved assumptions and judgments as to principal default and loss rates, prepayment rates, and market discount rates. The acquired loans were recorded at fair value at the acquisition date without carryover of Inland’s previously established allowance for credit losses. The fair value adjustment to acquired loans was a reduction to the carrying amount of $62.1 million. To estimate the fair value of the core deposit intangible, the Company utilized a discounted economic benefit methodology that involved assumptions such as deposit runoff rates, cost of deposits, cost of alternative funds, and a discount rate applied. The fair value of the core deposit intangible recorded was $17.3 million.

We identified the valuation of acquired loans and the valuation of the core deposit intangible as critical audit matters because of the judgment necessary by management to identify purchased loans with deteriorated credit quality since acquisition and to determine the fair value of the loan portfolio acquired and the fair value of the core deposit intangible recorded, and the related high degree of auditor judgment and the extensive audit effort involved in testing management’s significant estimates and assumptions, including using individuals with specialized skill and knowledge.

The primary procedures we performed to address this critical audit matter included:

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Testing the design, implementation and operating effectiveness of controls relating to the completeness and accuracy of acquired loan and deposit level data, and the fair value estimate of acquired loans and the core deposit intangible, including significant assumptions and methods utilized in the respective calculations.

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Testing the completeness and accuracy of acquired loan and deposit level data used in the fair value estimate calculations.

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Testing the completeness and accuracy of loans identified as purchase credit deteriorated since origination and evaluating identification criteria utilized by management.

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Utilizing our internal valuation specialists to:

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Test management’s approach to the fair value estimates for reasonableness.

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Validate the reasonableness of assumptions utilized in the determination of the fair value of acquired loans and core deposit intangible, including the principal default and loss rates, prepayment rates, market discount rates assumptions, and deposit rate and decay assumptions.

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Independently estimate the fair value of the acquired loans and core deposit intangible and compare it to the fair value recorded by management.

/s/ Moss Adams LLP

Portland, Oregon

March 4, 2024

We have served as the Company’s auditor since 2013.