Defense Contract Audit Agency (DCAA) audit standards require that employees who modify a submitted, rejected, or re-opened timesheet must enter change comments. Therefore, if your organization is DCAA compliant, you are required to enter comments for any changes they make to a timesheet after submission.

Also, Substitute users are required to enter comments for changes they make to another user's timesheet at any time (even prior to submission).
This comment will be included in an email sent to the timesheet owner to notify them of the change.