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.Fee adjustments must be made prior to the refund request to reflect an overpayment of the amount being refunded. 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. Have you recently received a notice of overpayment from social security? Our document template is designed to make the process of writing an "Inform a Customer of an Overpayment" letter quick, easy, and stress-free. The IRS uses Letter 3286C to inform you that they believe you may have overpaid for a particular year and will refund you the difference.