To help you out, we have provided sample letters that you can use to request waivers of several different types of IRS penalties. There are a multitude of penalty defenses against proposed or already assessed penalties.This Insight discusses some of those defenses. This guide provides a sample letter to IRS to waive penalty which will help you present your case and request relief from penalties. The failure to pay penalty applies if you don't pay the tax when due. The penalty you must pay is a percentage of the taxes you didn't pay. The forms listed below are PDF files. They include graphics, fillable form fields, scripts and functionality that work best with the free Adobe Reader.