If the certified mail is returned to you unclaimed, then submit the entire, unopened envelope and letter to. Report an overpayment.Complete an overpayment refund form to notify First Coast of an overpayment prior to receiving a demand letter. The Benefit Recovery Unit reviews the case and establishes a claim if an overpayment has indeed occurred. When we notify you of an overpayment you can make arrangements for repayment, appeal the decision, or request a waiver. You must appeal the overpayment within 90 days of the date on the notice. Keep a copy of your dated hearing request. Thank you for completing this Overpayment Refund. Do not use this form to make a payment to Social Security Administration for any reason other than to repay an overpayment.