Whether the overpayment notification letter to the customer is a system generated letter (Notice 18) or a manual letter it must state the following information:. The salary overpayment resulted because .To determine the overpayment amount take the "Amount Recvd" and subtract the "Right Amt". This amount will appear in the "Current Overpaid" column. The purpose of an overpayment demand letter is to notify the providers and suppliers of the existence and amount of an overpayment, and to request repayment. Complete this form if any of the following applies: You think that you are not at fault for the overpayment and you cannot afford to pay the money back. When claims are adjusted due to an overpayment, a Solicited Demand letter will be issued to you.