As part of internal audit ' s assistance with an annual external audit, the internal...

Bank confirmations are the most reliable source for verifying the current year-end bank balances. These confirmations are direct responses from the bank to the auditor, providing independent verification of the account balances as of the end of the year. This external confirmation is considered more reliable than internal documents like bank statements, reconciliations, or general ledger balances because it comes directly from a third-party source, ensuring its accuracy and completeness.

The Institute of Internal Auditors (IIA) - Practice Guide: External Confirmations

Auditing Standards (e.g., ISA 505 - External Confirmations)