A demand letter is an official notice requesting money, possession of assets, or action on a legal matter. Find out when is the right time to send a letter of demand if you have had no success in getting your invoice paid.In this post, we break down the anatomy of a demand letter so that you can create a compelling piece of communication that expedites cash recovery. Ask for payment simply. Leave emotion out of the email. If you need help filling it out, your caseworker will help you. We'll walk you through how to write a demand letter for payment below, with sample demand payment letters and tips for professional, effective messaging. Pay my probation fees or restitution? Contact my probation or pretrial officer? (a) My post office address is: (b) My residence address is: ; and.