An overpayment can happen if there is an ineligibility notice, which disqualifies a claimant in certain cases where they have already received benefits. 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. Report an overpayment. Complete an overpayment refund form to notify First Coast of an overpayment prior to receiving a demand letter. Florida law requires that refund applications be supported with sufficient information and documentation to determine eligibility and the refund amount due. Once the Cost Containment Unit (CCU) has reviewed the overpayment, you will receive a letter explaining the details of the reconciliation. The Notice of Overpayment will include information on how to appeal. You must appeal the overpayment within 90 days of the date on the notice. You have to tell your credit or debit card company about any error you're disputing within 60 days of when the first statement with the charge was sent to you.