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.Our document template is designed to make the process of writing an "Inform a Customer of an Overpayment" letter quick, easy, and stress-free. Overpayment Demand Letter - English. NCBI-29-Overpayment-Demand-Letter-English.pdf. PDF • 147.13 KB - November 12, 2019. Please include the last four digits of your Social Security Number or your Claimant ID with your payment. You have to tell your credit or debit card company about any error you're disputing within 60 days of when the first statement with the charge was sent to you. IMPORTANT: Please answer the following questions as completely as you can and submit any supporting documents with your waiver request. To designate part of your overpayment to the N.C. Education. Endowment Fund, see the instructions for Line 31 on Page 15.