Just call 555-5555 and our customer service representative will honor your request. Our document template is designed to make the process of writing an "Inform a Customer of an Overpayment" letter quick, easy, and stress-free.An overpayment may occur when a claimant is paid unemployment insurance benefits and is later found to not be eligible for those benefits. For ACTIVE faculty, staff and students for an overpayment in the Current Calendar Year. A statement or letter from the company indicating: (1) Property Index Number, (2) taxpayer's name,. If you would like to receive your overpayment as a refund, complete Lines 37 and 38. The IRS uses Letter 3286C to inform you that they believe you may have overpaid for a particular year and will refund you the difference.