What documentation must be retained for audit purposes concerning annual ratings?

The correct choice is the Performance Rating Form as it serves as the official documentation of an employee's annual performance review. This form contains critical information regarding the evaluation criteria, the scoring or rating assigned, comments from the supervisor, and any development plans put forth for the employee. Retaining this form is essential for compliance with auditing standards, ensuring that there is a verifiable record of performance assessments that can be reviewed for consistency and adherence to agency policies.

Personal notes may be helpful for a supervisor's reference during evaluations, but they are not standardized documentation and may lack the necessary formality required for audits. Previous evaluations can provide context for an employee’s performance over time, but they are not the primary document that illustrates the annual assessment for a specific year. Salary records relate to compensation rather than performance evaluation and do not fulfill the requirements for documenting annual ratings. Therefore, the Performance Rating Form is the ideal document to retain for auditing purposes concerning annual ratings.