Return receipt on Finally Closed PO

Hello;

We had finally closed a PO and now would like to return an outstanding receipt which was associated.  The receipt amount is an expense item which is forever showing on Uninvoiced receipt report.  The supplier has provided a credit memo, however error message received when receipt information entered.  How do we remove the item from the accrual report and how do we prevent a PO to be finally close when there are outstanding receipt items?

APP-SQLAP-10716 : This purchase order line has been final closed. You may want to review the purchase order before continuing the match.