What this notice is about You didn't file your return by the due date. What you need to do Send us the amount due by the date on the notice to avoid interest charges. You may want to If you think you may have reasonable cause for filing your return late, you need to provide a signed explanation outlining the circumstances which resulted in not filing your return timely. Refer to the “Removal or reduction of penalties” section on your notice. See more about penalties. Frequently asked questions Q. What if I disagree with the penalty? A. Send a written statement outlining the circumstances which resulted in not filing your return timely. Reference Tools Publication 5027, Identity Theft Information for Taxpayers Full list of tax forms and instructions Need Help? You can authorize someone to contact the IRS on your behalf. See if you qualify for help from a Low Income Taxpayer Clinic. If you can’t find what you need online, call the IRS number at the top of your notice or letter.