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. Fill out and submit this form. Call toll free: 1-800-743-8525 or for hearing or speech impaired use TDD 1-800-952-8349. The salary overpayment resulted because . Dropping classes or failing to attend can result in a financial aid overpayment.