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. The salary overpayment resulted because . An overpayment is when you receive benefits you are not eligible for. For multiple CWES overpayments, follow the order of priority per CalWORKs Handbook Section 51.6.7. In Benefit Overpayment Services, you can make a payment, view past payments, and set up an installment agreement to make monthly payments.