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.To avoid collections, you must repay your overpayment balance in full. If you cannot repay the balance in full, you may enter into a payment agreement with DES. The salary overpayment resulted because . Child Support Services (CSS) are available to anyone who needs help collecting child support through a network of state and locally run offices. How do I apply for Child Support Services? You can complete the application at your local CSS office or apply online. Overpayment Inquiries. This memorandum serves as notification of an overpayment of wages that you received and the subsequent repayment that is your responsibility.