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.Our document template is designed to make the process of writing an "Inform a Customer of an Overpayment" letter quick, easy, and stress-free. Utah Taxpayer Advocate Service. The Taxpayer Advocate Service helps taxpayers who have made multiple, unsuccessful attempts to resolve concerns with the Tax. We have identified the following overpayment and are in good faith voluntarily refunding all monies collected in error. The salary overpayment resulted because . Salt Lake City, UT 84131-0364.