Follow these 10 tips to write overdue payment letters for requesting outstanding payments from your late paying customers. Recovering overdue funds from customers is frustrating.These overdue invoice letter templates show you the right tone and language to use. We've created ready-to-use collection letter templates. Read on below to find out what every letter should say in order to collect payment as soon as possible. Below, we've created an example of a debt settlement proposal letter that you can use as a guide. Your letter can be sent via your preferred contact method. What should be included in a demand letter? Stop chasing clients for payment. 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.