Formal:
* Auditee: This is the most common and formal term. It clearly indicates the person or entity being audited.
* Subject of the audit: This phrase emphasizes the focus of the audit.
Informal:
* The person being audited: This is the most straightforward and common way to describe the individual in informal settings.
* The one under review: This phrase emphasizes the scrutiny of the audit.
The best term to use will depend on the specific situation and audience.