I apologize for the lateness of this order. It is not the way we like to treat our valued customers.Begin your apology letter with a sincere statement apologizing for your action or mistake. Don't know how to write an apology letter to customer? This letter of apology guides students to explain what they did, how that made others feel, and what they should have done instead. We have advice on writing letters of apology plus sample letters for personal, school, and business situations. Here are the 10 most popular Apology Letters:. Learn how to craft an effective apology letter to a customer. Explore our guide, templates, and best practices for customer service recovery. Teach your students how to apologize with this fun craft, apology letter templates, and a full class apologizing activity anchor chart!