The most effective time for an internal auditor to develop a risk and control matrix is during the planning phase of an audit engagement. This matrix helps in identifying the key risks and the controls in place to mitigate those risks, which is crucial for developing a focused and effective engagement work program.
IIA Reference:
IIA Standard 2201: Planning Considerations requires internal auditors to consider significant risks and controls when planning the engagement. Developing a risk and control matrix at this stage ensures that the audit work is appropriately targeted at the most critical areas.
The Practice Guide on Risk Assessment advises that creating a risk and control matrix during planning helps in structuring the audit to address identified risks effectively.