The IRS charges two separate penalties when you file after the deadline

If you file your federal tax return after April 15 (or the extended deadline if you requested one), the IRS charges a failure-to-file penalty and a failure-to-pay penalty if you owe taxes. These are calculated differently and stack on top of each other. The failure-to-file penalty is usually steeper, so filing even a few days late costs more than paying late once you've filed.

The failure-to-file penalty is 5% of the unpaid taxes for each month or part of a month that your return is late, up to a maximum of 25%. The failure-to-pay penalty is 0.5% of unpaid taxes per month, also capping at 25%. If you file on time but pay late, you only owe the failure-to-pay penalty. Both penalties accrue interest on top of the original tax amount, compounded daily at a rate the IRS sets quarterly.

The IRS does not charge penalties if you filed on time but the payment itself was late — only if the return itself arrives after the deadline. This is why filing electronically and requesting an extension before April 15 matters: an extension moves your filing deadline to October 15, and penalties do not start until after that date.

Key Takeaways

  • The failure-to-file penalty is 5% per month of unpaid taxes, up to 25%, and applies only if your return arrives after the deadline.
  • The failure-to-pay penalty is 0.5% per month of unpaid taxes, up to 25%, and applies whether you file on time or late.
  • Filing late costs more than paying late because the failure-to-file penalty is ten times larger per month than the failure-to-pay penalty.
  • Requesting a filing extension before April 15 moves your deadline to October 15 and delays when penalties begin to accrue.
  • Interest accrues daily on all unpaid taxes and penalties at a rate set by the IRS each quarter, currently around 8% annually.

How the failure-to-file penalty is calculated

The failure-to-file penalty starts at 5% of your unpaid tax liability for the first month your return is late. If you file two months late, the penalty is 10%. The penalty continues to grow by 5% for each additional month until it reaches 25% of the unpaid amount, at which point it stops growing. A return filed six months late or more will have the full 25% penalty applied.

The IRS counts any part of a month as a full month. If you file one day after the deadline, that counts as one month. If you file 31 days late, that still counts as one month. Once you cross into the next calendar month, the second month of lateness begins. This means the difference between filing on April 16 and April 30 is the same penalty — both are one month late.

The penalty is calculated on the amount of tax you actually owe, not on your total income or the size of your refund. If you are owed a refund, there is no failure-to-file penalty, though you will lose interest the government would have paid you on that refund if you had filed on time.

How the failure-to-pay penalty works

The failure-to-pay penalty is 0.5% of unpaid taxes per month, capping at 25% total. This penalty applies whether you file on time or late. If you file your return on April 10 but do not pay the taxes you owe until July, you owe three months of failure-to-pay penalties (0.5% × 3 = 1.5% of the unpaid amount).

The failure-to-pay penalty accrues more slowly than the failure-to-file penalty, but it never goes away until the debt is paid. If you owe $5,000 and do not pay for a year, the failure-to-pay penalty alone is $600 (12 months × 0.5% × $5,000). The IRS will not remove this penalty even if you eventually pay, unless you have a valid reason for the delay — such as a serious illness or a natural disaster — and you request penalty relief in writing.

If you file late and pay late, both penalties apply. The failure-to-file penalty stops growing once you file, but the failure-to-pay penalty continues until you pay in full.

When penalties do not apply

You do not owe a failure-to-file penalty if you filed your return on time, even if you pay the taxes late. You also do not owe either penalty if you are owed a refund, because there is no unpaid tax liability. If your return shows you overpaid throughout the year and the IRS owes you money, filing late does not trigger penalties.

The IRS may waive penalties if you have a reasonable cause for filing or paying late. Reasonable cause includes serious illness, death in the family, a natural disaster, or reliance on incorrect advice from a tax professional. You must request this relief in writing and provide documentation of the reason. The IRS does not automatically grant relief — you have to ask and explain.

If this is your first time filing late and you have a clean record for the past three years, the IRS has an automatic relief provision called first-time penalty abatement. You can request this by phone or in writing, and the IRS will remove one set of failure-to-file and failure-to-pay penalties from your account. This applies only once in your lifetime.

Interest on unpaid taxes and penalties

Interest accrues on any unpaid tax balance starting the day after the original deadline, regardless of whether you file on time. The interest rate is set by the IRS each quarter and is tied to the federal short-term interest rate plus 3%. As of early 2024, the rate is approximately 8% per year, but it changes quarterly and varies based on when the debt originated.

Interest compounds daily, meaning you owe interest on the interest. A $5,000 unpaid tax balance will cost roughly $400 in interest alone after one year, plus the penalties on top. The longer you wait to pay, the more the total debt grows. Unlike penalties, interest cannot be waived or removed by the IRS — it is a mandatory charge on all unpaid federal taxes.

The IRS sends a bill (called a notice of assessment) showing the original tax, penalties, and interest owed. This bill includes a deadline to pay or request a payment plan. If you do not respond, the IRS can place a lien on your property or garnish your wages.

How to request an extension and avoid penalties

You can request an automatic six-month extension by filing Form 4868 (Application for Automatic Extension of Time to File U.S. Individual Income Tax Return) before April 15. This moves your filing deadline to October 15 and delays when the failure-to-file penalty begins. You do not need a reason to request this extension — the IRS grants it automatically if you file the form on time.

An extension to file is not an extension to pay. If you owe taxes, they are still due on April 15, even if you have an extension to file. If you do not pay by April 15, the failure-to-pay penalty starts accruing immediately. To avoid this, estimate what you owe and pay it by the original deadline, then file your actual return by October 15.

You can file Form 4868 electronically through tax software, by mail, or by phone. If you file electronically, you get confirmation immediately. If you mail it, send it before April 15 and keep a copy for your records. Filing the extension form does not cost anything.

What to do if you have already filed late

If you have already filed late, you owe the penalties and interest described above. The IRS will calculate them and include them on your bill. You can pay the full amount, set up a payment plan, or request penalty relief if you believe you have reasonable cause.

To request penalty relief, write a letter to the IRS explaining why you filed late. Include copies of supporting documents — medical records for illness, death certificates for a death in the family, or correspondence from a tax professional if you relied on their advice. Mail this letter to the IRS address shown on your bill. The IRS typically responds within 30 days, though it can take longer.

If you cannot pay the full amount, you can request an installment agreement (payment plan) by calling the IRS or submitting Form 9465 (Installment Agreement Request). The IRS charges a setup fee for this, usually between $31 and $225 depending on how you set it up. Interest and penalties continue to accrue while you are on a payment plan.

Frequently Asked Questions

How much will I owe if I file one month late?

You will owe 5% of your unpaid tax liability as a failure-to-file penalty, plus 0.5% as a failure-to-pay penalty if you have not paid by the deadline. You will also owe interest at roughly 8% per year, compounded daily. On a $3,000 tax bill, one month late costs approximately $165 in penalties and interest combined.

Does an extension protect me from penalties?

An extension protects you from the failure-to-file penalty only. It does not protect you from the failure-to-pay penalty. If you owe taxes, you must pay by April 15 even if you have an extension to file. Paying by April 15 and filing by October 15 avoids both penalties.

Can the IRS remove penalties if I have a good reason?

Yes, if you request penalty relief and provide documentation of reasonable cause — illness, death, natural disaster, or reliance on professional advice. You must request this in writing. If you have never been late before in the past three years, you may also request first-time penalty abatement, which the IRS grants automatically once in your lifetime.

What if I owe a refund instead of taxes?

You do not owe any penalties if you are owed a refund. However, you will lose interest the government would have paid you on that refund. Filing late reduces the interest you receive, so it is still worth filing as soon as you can.

Does interest ever stop accruing?

No. Interest accrues daily on all unpaid federal taxes until the debt is paid in full. It cannot be waived or removed. The only way to stop interest is to pay the tax bill.