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.The salary overpayment resulted because . This memorandum serves as notification of an overpayment of wages that you received and the subsequent repayment that is your responsibility. Fill out and submit this form. Call toll free: 1-800-743-8525 or for hearing or speech impaired use TDD 1-800-952-8349. Navigate to the Invoice. Click the Select check box next to the payment at the bottom of the invoice.