During the filework phase of an assurance engagement the internal auditor decides that she wants...

If an internal auditor decides to adjust the audit work program during the fieldwork phase of an assurance engagement, the most appropriate next step is to obtain approval from the engagement supervisor. This ensures that any changes to the scope or procedures are reviewed and sanctioned by the audit management, maintaining the integrity and alignment of the audit objectives.

IIA Standards: 2240 - Engagement Work Program

IIA Practice Guide: Engagement Planning