This document discusses best practices for writing collection letters to customers with past due accounts. It notes that collection letters should be persuasive rather than forceful in order to get payment while maintaining goodwill. The purpose of collection letters is to collect money owed, keep the customer, and build goodwill. The document outlines a series of collection letters that start mild but become more insistent if payment is not received. It provides examples of language for a friendly reminder, request for explanation, appeal for payment, and final collection letter before legal action. Throughout, the letters should remain courteous while firmly requesting payment by a specified deadline.