Banking · Information Systems Audit

A large private bank is planning to migrate its Core Banking System (CBS) from an on-premise data center to a public cloud environment. During the User Acceptance Testing (UAT) phase, the accounts department discovers that the new cloud system calculates compound interest on a monthly basis, whereas the legacy system used daily compounding logic for certain corporate deposits. This discrepancy results in a 0.5 percent difference in the interest expense. Furthermore, the Audit Trail module in the cloud version is configured to purge logs every 30 days to save storage costs, which conflicts with the bank's policy of retaining logs for 10 years. As the Head of Internal Audit, which of the following is the most critical recommendation?