The IRS charges two separate penalties when you miss a tax important date: a failure-to-pay penalty and interest on the unpaid amount

The failure-to-pay penalty is 0.5% of your unpaid taxes for each month or part of a month that the payment is late. This penalty starts the day after the important date and continues to accrue until you pay in full. If you owe $5,000 and pay 60 days late, you will owe a penalty of $50 (0.5% × $5,000 × 2 months).

Interest is separate from the penalty. The IRS charges interest on both your unpaid taxes and the penalties themselves. The interest rate changes quarterly and is currently set at the federal short-term rate plus 3%. For 2024, the rate is 8% per year, compounded daily. Interest accrues from the original due date until you pay.

The failure-to-pay penalty caps at 25% of your unpaid taxes. Once you reach that ceiling, the penalty stops growing even if you remain unpaid. Interest, however, has no cap and will continue to accrue indefinitely.

Key Takeaways

  • The failure-to-pay penalty is 0.5% per month, starting the day after your tax important date, and stops at 25% of what you owe.
  • Interest accrues on unpaid taxes and penalties combined, at a rate that changes quarterly and currently sits at 8% per year.
  • A payment made 90 days late will incur roughly 4.5% in penalties plus interest, meaning a $10,000 debt costs you approximately $1,200 in penalties and interest over one year.
  • The IRS may add a separate failure-to-file penalty if you did not file your return on time, which is 5% per month up to 25%.
  • Paying even a partial amount before the important date can reduce the total penalty, since the 0.5% monthly rate applies only to the unpaid balance.

How the 0.5% monthly penalty works in practice

The failure-to-pay penalty accrues on whatever amount remains unpaid. If you owe $10,000 and pay $3,000 on the due date, the penalty applies only to the remaining $7,000. Each month that passes adds 0.5% of that $7,000 to what you owe the IRS.

The penalty is calculated on a daily basis but rounded to the nearest month. If you pay 45 days late, you are charged for one full month. If you pay 46 days late, you are charged for two months. This means paying on day 46 costs significantly more than paying on day 45, even though the difference is one day.

Once your total penalty reaches 25% of the original unpaid amount, it stops growing. If you owe $10,000 and the penalty reaches $2,500, no additional failure-to-pay penalty will accrue no matter how long you wait. Interest, however, continues to compound on both the tax and the penalty.

Interest compounds daily and has no upper limit

Interest is calculated on your unpaid tax balance plus any penalties that have accrued. The IRS compounds interest daily, meaning you pay interest on the interest itself. The rate is set quarterly by the IRS and is published in advance. For the first quarter of 2024, the rate was 8% per year; rates vary by quarter and have ranged from 3% to 10% in recent years.

A $10,000 unpaid tax debt at 8% annual interest costs roughly $800 in interest alone over one year, assuming no penalties. Add the failure-to-pay penalty of 6% (12 months × 0.5%), and your total cost is approximately $1,400 after one year. After two years, interest compounds to roughly $1,664, and the penalty caps at $2,500, bringing your total debt to approximately $14,164.

Interest accrues whether or not you have filed your return. If you have not filed, the IRS will estimate your tax liability and begin charging interest on that estimate. Once you file, the interest recalculates based on your actual liability, but the accrual date remains the original due date.

The failure-to-file penalty is separate and stacks on top

If you did not file your tax return by the important date, the IRS charges a failure-to-file penalty in addition to the failure-to-pay penalty. This penalty is 5% of your unpaid taxes for each month or part of a month that your return is late, up to a maximum of 25%. If both penalties explore, the IRS subtracts the failure-to-pay penalty from the failure-to-file penalty so you do not pay both at full strength, but the combined penalty is still substantial.

For example, if you file 90 days late and pay 90 days late, you owe a 15% failure-to-file penalty (5% × 3 months) and a 4.5% failure-to-pay penalty (0.5% × 9 months, rounded). The IRS applies the 4.5% failure-to-pay penalty first, then adds the difference between the two, resulting in a combined penalty of 15%. You do not pay both penalties in full.

Filing your return even if you cannot pay stops the failure-to-file penalty from accruing further. Only the failure-to-pay penalty continues to grow. This is why the IRS recommends filing on time even if you cannot pay the full amount due.

Penalties and interest when you set up a payment plan

If you owe more than you can pay when ready, the IRS offers payment plans called installment agreements. Setting up a plan does not erase the penalties and interest you have already accrued, but it stops additional failure-to-pay penalties from accruing once you are in compliance with the plan. Interest continues to accrue on the remaining balance.

For short-term plans (120 days or less), there is a one-time setup fee of $31 to $225 depending on how you set up the plan. For long-term plans (more than 120 days), the fee is $31 to $225 as well, plus interest continues to compound on the full remaining balance. A payment plan does not reduce what you owe in penalties; it only prevents new penalties from accruing while you are making regular payments.

If you miss a payment on your installment agreement, the failure-to-pay penalty resumes accruing on the unpaid balance. The IRS will notify you, and you have the opportunity to bring the account current or request a new agreement.

Circumstances that may reduce or remove penalties

The IRS has authority to remove or reduce penalties in specific situations. Reasonable cause is the standard the IRS uses. This includes serious illness, death in the family, unavoidable absence, or reliance on a professional tax preparer who made an error. The IRS does not automatically grant reasonable cause; you must request it and provide documentation.

First-time penalty abatement is a one-time removal of penalties if you have no penalties in the prior three years and your account is otherwise in good standing. You can request this by phone, mail, or in person at an IRS office. The request must be made within a reasonable time after the penalty is assessed.

Penalties are not removed for straightforward inability to pay. If you cannot afford to pay, a payment plan or offer in compromise may help, but the penalties themselves remain. Interest is never removed or reduced; it accrues until the debt is paid in full.

How to calculate what you will owe

To estimate your total debt, start with the original unpaid tax amount. Multiply that by 0.5% for each month late (up to 25% maximum). Then calculate interest at the current quarterly rate, compounded daily on the tax plus penalties. The formula is complex because interest compounds, but the IRS provides a penalty and interest calculator on its website.

For a rough estimate: a $5,000 unpaid tax at 8% annual interest, paid 6 months late, costs approximately $200 in penalties (0.5% × 6 months × $5,000) and $200 in interest, for a total of $5,400. After one year, the same debt costs approximately $400 in penalties and $400 in interest, for a total of $5,800.

The IRS sends a notice showing the exact penalty and interest owed. You can also call the IRS at 1-800-829-1040 to request a breakdown of your account, or view it through your IRS online account if you have registered for one.

Frequently Asked Questions

Can I negotiate the penalty amount with the IRS?

You cannot negotiate the penalty down, but you can request removal or reduction based on reasonable cause. This requires documentation—medical records for illness, death certificates for family loss, or proof that a tax professional made the error. The IRS reviews each request individually. First-time penalty abatement may also explore if you have no prior penalties in three years.

Does the penalty stop growing if I set up a payment plan?

The failure-to-pay penalty stops accruing once you are in an active installment agreement and making on-time payments. Interest continues to accrue on the remaining balance. If you miss a payment, the failure-to-pay penalty resumes.

What happens if I pay the tax but not the penalties and interest?

The IRS treats the tax, penalties, and interest as a single debt. You cannot pay only the tax and ignore the rest. Your payment is applied first to the tax, then to penalties, then to interest, in that order. You remain liable for whatever portion is unpaid.

Is there a maximum penalty I will ever owe?

The failure-to-pay penalty caps at 25% of your unpaid tax. Interest has no cap and will continue to accrue indefinitely until you pay. If you owe $10,000, the maximum failure-to-pay penalty is $2,500, but interest could eventually exceed the original tax amount if the debt remains unpaid for years.

Do penalties explore if I file late but pay on time?

Yes. The failure-to-file penalty applies if your return is late, even if you pay the tax owed by the original important date. The penalty is 5% per month up to 25%. Filing on time is separate from paying on time, and both important date carry their own penalties.