Significant accounting policies (Policies)

9 Months Ended

Sep. 30, 2025

Accounting Policies [Abstract]

Basis of Accounting

The consolidated interim financial statements of the Company were compiled in accordance with GAAP using the accounting policies set forth in note 1 of Notes to Financial Statements included in M&T's 2024 Annual Report. The financial statements contain all adjustments which are, in the opinion of management, necessary for a fair statement of the Company's financial position, results of operations and cash flows for the interim periods presented.

The following table provides a description of accounting standards applicable to M&T but not yet adopted at September 30, 2025.

Recent accounting developments

Standard	Description	Required date of adoption	Effect on consolidated financial statements
Standards not yet adopted as of September 30, 2025
Income Taxes - Improvements to income tax disclosures	The standard requires enhanced disclosures in the notes to financial statements including income taxes paid by jurisdiction (federal, state, foreign) and a tabular rate reconciliation between the reported amount of income tax expense (or benefit) and the amount of statutory federal income tax at current rates.	December 31, 2025	The Company intends to make the required disclosures of the amended guidance in its consolidated financial statements for the year ended December 31, 2025.
Income Statement - Expense disaggregation disclosures	The standard requires disclosure in the notes to financial statements of specified information about certain cost and expense captions on the income statement.	January 1, 2027	The Company does not expect the guidance will have a material impact on its consolidated financial statements.
Targeted improvements to the accounting for internal-use software	The standard eliminates the concept of a software development project stage such that the guidance is agnostic to different software development methods and introduces a new threshold for cost capitalization. The standard also provides factors to consider when determining whether significant development uncertainty exists.	January 1, 2028	The Company is evaluating the impact of the standard but does not expect the guidance will have a material impact on its consolidated financial statements.