Penalty
A charge imposed by the IRS for filing late, paying late, or underpaying estimated taxes. Common penalties include failure-to-file (5% per month) and failure-to-pay (0.5% per month).
IRS penalties are charges added to your tax bill when you fail to comply with filing and payment requirements. The most common are the failure-to-file penalty (5% of unpaid tax per month, up to 25%), the failure-to-pay penalty (0.5% of unpaid tax per month, up to 25%), and the estimated tax underpayment penalty.
The failure-to-file penalty is much steeper than the failure-to-pay penalty, so if you cannot pay your full tax bill, you should still file your return on time (or request an extension) to avoid the larger penalty. The IRS also charges interest on unpaid taxes, compounded daily, at the federal short-term rate plus 3%.
The estimated tax underpayment penalty applies when you do not pay enough throughout the year through withholding and estimated payments. Meeting the safe harbor — paying at least 100% of prior-year tax (110% if AGI over $150,000) or 90% of current-year tax — avoids this penalty. The IRS may waive penalties in cases of reasonable cause, such as a natural disaster or serious illness, if you request relief.
How it works
IRS penalties are added charges for not meeting filing, payment, or estimated tax obligations, and the two most common ones work very differently: the failure-to-file penalty runs 5% of unpaid tax per month up to a maximum of 25%, while the failure-to-pay penalty runs a much smaller 0.5% of unpaid tax per month, also capped at 25%. Interest, calculated separately at the federal short-term rate plus 3% and compounded daily, applies on top of either penalty.
You encounter these penalties as line items the IRS calculates and bills you for after processing your return, or through a notice if an estimated tax underpayment is detected. Because the failure-to-file penalty is ten times steeper than the failure-to-pay penalty, the practical lesson is to always file on time — or request an extension — even if you cannot pay the full balance owed; filing late is punished far more harshly than paying late.
A separate penalty applies specifically to underpaying estimated tax throughout the year, distinct from failing to pay a balance at filing time — this one is avoided by meeting safe harbor, generally paying at least 100% of the prior year's liability, 110% for higher earners, or 90% of the current year's actual liability across the year. The IRS can also waive penalties for reasonable cause, such as a natural disaster, serious illness, or other circumstances beyond your control, if you formally request relief.
Example: failure-to-file versus failure-to-pay
A taxpayer owes $4,000 and neither files nor pays anything by April 15, filing three months late with no extension requested and no payment made until filing.
The failure-to-file penalty alone comes to 5% per month for three months, or 15% of the $4,000 owed — $600. Had they at least filed on time and only failed to pay, the penalty for those same three months would have been just 0.5% per month, or $60, showing why filing on time matters even without full payment.
Frequently asked questions
What's the difference between failure-to-file and failure-to-pay penalties?
Can the IRS waive a penalty?
Does interest keep adding up even after a penalty is charged?
Related Terms
Safe Harbor
IRS rules that protect you from underpayment penalties if you pay at least 100% of the prior year's tax (110% if AGI over $150,000) or 90% of the current year's tax.
Extension
A request to push your tax return filing deadline from April 15 to October 15. An extension gives more time to file but not more time to pay any taxes owed.
Quarterly Estimated Tax
Tax payments made four times a year by self-employed individuals and others with income not subject to withholding. Due dates are April 15, June 15, September 15, and January 15.
Tax Return
The form(s) you file with the IRS to report income, claim deductions and credits, and calculate your tax liability or refund. For individuals, this is Form 1040.