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.A refund letter to a customer should be structured to convey the necessary information clearly, empathetically, and respectfully. We'll walk you through the steps for creating an incorrect payment letter, as well as provide you with some templates you can use. The salary overpayment resulted because . In this article, we'll provide tips on how to handle refund request letters and 7 sample templates you can use to get started today! How do you write a letter to inform of a double payment? Providers have the option to submit a Request For Extended Repayment Schedule (ERS). A complete ERS request should be submitted immediately.