You can find the CP or LTR number on the right corner of the letter. Sending an IRS audit reconsideration request?How to Write a Client Letter for a Tax Issue. In this article, we will provide you with a detailed guide on the steps involved in writing a letter to the IRS. Send a typewritten letter to the IRS office that sent the notice. Use the format in the sample letter below. IRS letters are computer generated and follow a time line set in the database. Often a response may cross in the mail with a second notice. Corrected spelling and grammatical errors. Corrected references, citations and links.