How To Write A Formal Apology Letter To A Customer . Acknowledge that it was you who screwed up the order or failed to respond to a complaint “in a timely manner.”. Here are some simple steps you can follow to help you write an effective apology letter: 15+ Apology Letter Templates MS Word, Excel & PDF Formats, Samples from www.wordpdftemplates.com This can be to apologies for a long range of issues including poor services. At abc company, we take pride in meeting the expectation of our clients. A customer is likely to forgive you when you write an apology letter as it shows remorse and adds a personal touch.