Tell them that they have "overpaid" you. Then ask them to ring you for details.Respond to customer refund requests professionally with these templates. There has been an error in your favor! NOTICE OF FOOD STAMP OVERPAYMENT (DEMAND LETTER) (Timely and Adequate). NOTICE. The Tax Office holds unclaimed property tax overpayments made within the last three years and outstanding (uncashed) refund checks. A copy of that letter is enclosed. The salary overpayment resulted because . In a simple savings account. Then when they catch their mistake.