IRS Penalties and Interest: How They Calculate and How to Fight Them

IRS Problems · IRS HELP

The IRS charges penalties and interest that can double your original tax bill over time. Here's how each penalty works, how interest accrues, and how to request relief through first-time abatement or reasonable cause.

Many taxpayers are surprised to find that by the time they deal with an IRS notice, the original tax bill has grown significantly — sometimes doubled — from penalties and interest. Understanding how these charges work, and knowing that the IRS will often remove them if you ask correctly, can save you thousands of dollars.

The Three Most Common IRS Penalties

1. Failure-to-File Penalty (FTF): 5% of unpaid tax per month (or partial month), up to 25% of the total unpaid tax. If your return is more than 60 days late, the minimum penalty is the lesser of $510 (2025) or 100% of unpaid tax. This is the most expensive penalty — always file on time, even if you can't pay.

2. Failure-to-Pay Penalty (FTP): 0.25–0.5% of unpaid tax per month, up to 25%. Lower rate if an installment agreement is in place. This penalty continues until the tax is fully paid.

3. Accuracy-Related Penalty: 20% of the underpayment if caused by negligence, disregard of rules, or substantial understatement of income. Applied when the IRS audits and finds you understated tax by more than $5,000 or 10% of the correct tax.

How IRS Interest Works

Interest accrues on unpaid tax from the original due date of the return until the balance is paid in full. For 2025, the underpayment rate is the federal short-term interest rate plus 3 percentage points — currently around 7–8% annually, compounded daily.

Interest also accrues on unpaid penalties. There is no cap on interest accumulation. A $10,000 tax debt unpaid for 3 years can easily become $14,000–$16,000 with penalties and interest combined.

Unlike penalties, the IRS generally does not remove interest (it's statutory). The only way to stop interest is to pay the balance — or pursue an Offer in Compromise.

First-Time Abatement (FTA): The Easiest Path to Penalty Relief

The IRS offers First-Time Abatement (FTA) as an administrative waiver for taxpayers with a clean compliance history. You qualify if:
• You have no penalties for the prior 3 tax years
• You have filed all required returns (or a valid extension)
• You have paid, or arranged to pay, any tax due

FTA applies to failure-to-file, failure-to-pay, and failure-to-deposit penalties. It can be requested by phone (call the number on your notice) or in writing. You don't need to explain why you were late — FTA is automatic if you meet the criteria.

FTA is available once every 3 years and can eliminate thousands of dollars in penalties with a single phone call.

Reasonable Cause Penalty Relief

If you don't qualify for FTA — or have penalties beyond FTA's scope — you can request abatement based on 'reasonable cause': circumstances beyond your control that prevented timely filing or payment.

Examples the IRS accepts:
• Serious illness (you or an immediate family member)
• Natural disaster, fire, or casualty
• Death in the immediate family
• Unavoidable absence (incarceration, hospitalization)
• Reliance on erroneous IRS advice
• Failed tax professional (with documentation)

You must write a detailed explanation and provide supporting documentation. Vague explanations ('I forgot') are almost always denied. An enrolled agent can draft a compelling reasonable cause letter.

How to Request Penalty Abatement

By phone: Call the IRS number on your notice and ask for FTA. This takes 15–30 minutes and works well for simple cases.

By mail: Write a penalty abatement request letter citing the specific penalty notice number, the tax period, the type of relief you're requesting (FTA or reasonable cause), and your supporting facts and documents.

Form 843: Use this form for a formal written claim for refund of penalty and interest already paid.

If denied: You can appeal the denial through the IRS Office of Appeals. An enrolled agent can represent you throughout this process.

Frequently Asked Questions

If I file late but owe nothing, is there a penalty?

No penalty if you're owed a refund and file late. There's also no penalty if your balance due is zero. However, you have only 3 years from the original due date to claim a refund — wait too long and you forfeit it.

Can I get both FTA and reasonable cause relief on the same penalty?

No — you can only use one basis for abatement per penalty. Start with FTA (it's easier). If you don't qualify for FTA, pursue reasonable cause.

The IRS says I owe penalties from 5 years ago. Can they still collect?

The IRS has 10 years from the date of assessment to collect a tax debt (the Collection Statute Expiration Date, or CSED). Entering a payment plan, filing for bankruptcy, or requesting an OIC tolls (pauses) this clock. An enrolled agent can calculate your CSED and advise whether collection is still active.

I set up a payment plan. Do penalties still accrue?

Yes. A payment plan stops collection action (levies, garnishments) but does not stop the failure-to-pay penalty or interest from accruing. They continue until the full balance is paid.