The Tax Office holds unclaimed property tax overpayments made within the last three years and outstanding (uncashed) refund checks. Just call 555-5555 and our customer service representative will honor your request.The MAC sends an overpayment determination demand letter within 7 calendar days. For ACTIVE faculty, staff and students for an overpayment in the Current Calendar Year. This memorandum serves as notification of an overpayment of wages that you received and the subsequent repayment that is your responsibility.