If an audit has been closed and confirmed, you do have the option to open it again to edit and send back to your supplier. 

Step 1: Sign in, go to the supplier audit manager then select the audit you want to Reopen, then select Reopen Audit

Step 2: The audit has been reopened. You will see this notification and the status reverts to Requires your Action, were you are back to the steps above to complete and send