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.For other questions you may have, please contact the Office of the Tax Assessor-Collector at for personalized assistance. 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 salary overpayment resulted because . You may fill out the change of address form or simply make the request in writing. We have identified the following overpayment and are in good faith voluntarily refunding all monies collected in error. Complete the Customer Information and Payment Information.