Quickbooks desktop How to clear a customer overpayment from open invoices after creating a credit memo and refund check
When you created the Credit Memo, you Duplicated the value that already exists from the overpayment.
The overpayment screen already has the bottom left Radio button for Issue the refund.
You need to Delete your Credit Memo; that will leave you with the AR check to the customer. Now open Receive Payment for that name, leave the amount as 0, and apply the existing credit to this refund check.