Which source of information offers the highest level of reliability to an internal auditor?

Bank confirmations provide a high level of reliability to internal auditors because they originate from an independent third party, which minimizes the risk of bias and inaccuracy typically associated with internal sources. This external verification allows the auditor to confirm the authenticity of cash balances or transaction details directly from the bank, enhancing the trustworthiness of the information.

In contrast, supplier invoices, while useful, can be influenced by the vendor's own inaccuracies or biases. Management interviews are valuable for understanding perspectives and insights but can be subjective and may lack verification. Transaction logs, although helpful for validating operational activities, are still internal documents that could potentially be altered or manipulated. Overall, the independent nature of bank confirmations makes them a more reliable source for auditors in assessing financial health and transaction integrity.