This brief but important letter notifies a customer that he or she has overpaid you. It can serve as a very good customer relations letter.Select Benefit Overpayment Services. Step 1: To file a Request for Waiver, fill out form SSA-632-BK, called a. "Request for Waiver of Overpayment Recovery. This program will help you write a letter that formally requests the money you are owed. This is called a Demand Letter. To access the forms below, you will need Adobe Acrobat Reader. Note: Receipts must be received within 30 calendar days after the issuance to avoid an overpayment. If mailing, please keep a copy of the receipts mailed.