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.The salary overpayment resulted because . We have identified the following overpayment and are in good faith voluntarily refunding all monies collected in error. This memorandum serves as notification of an overpayment of wages that you received and the subsequent repayment that is your responsibility. Administration mails the notification of overpayment letter to the affected employee. The overpayment can be due to your recent receipt of deductible income from a source considered offsetable under your policy.