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.Commonly Used Forms​​ Fill out and complete the PDF to order a copy of a Business Certificate. Fill out and complete the PDF to order a copy of a Deed. If you have an active case, contact your worker if you would like to pay back more than what you are paying each month. Fill out a simple, secure Demand Letter questionnaire and Courtlinked handles all the legal form filing work. An overpayment of benefits can occur for a number of reasons. Knowing how they can occur can help you avoid such a circumstance. A demand letter is an official notice requesting money, possession of assets, or action on a legal matter.