The most reliable follow-up procedure to determine if management has resolved the finding of non-sequential purchase order numbers is to inspect the system settings and transaction logs to determine if sequential order numbers are generated. This will provide direct evidence of the system’s functionality and compliance with the audit recommendation. The other options are less reliable because they rely on indirect evidence or information obtained from management, which may not be accurate or complete. References: CISA Review Manual (Digital Version), Standards, Guidelines, Tools and Techniques