Underpaid estimated tax: the penalty and the safe harbors

The estimated tax penalty is small compared with most IRS penalties, but it is charged automatically and often avoidable. This guide explains how it works and the safe harbors that protect you.

By Hamza Fida, Chartered Accountant. Reviewed by Muhammad Bilal, Chartered Accountant. Checked against official sources on . 2 minute read.

Short answer

The underpayment penalty safe harbor rules let you avoid the estimated tax penalty by paying enough during the year. Individuals are safe if they owe less than $1,000, or paid at least 90% of this year's tax or 100% of last year's, 110% if last year's income was over $150,000. The penalty works like interest on each late or short payment.

At a glance

Individuals owe less than
$1,000: no penalty
Current-year safe harbor
90% of this year's tax
Prior-year safe harbor
100% of last year's tax, 110% if AGI over $150,000
Penalty rate
Federal short-term rate plus 3 points, per late installment
Uneven income
Annualized income method on Form 2210
Corporations
Owe $500 or more; Form 2220
Underpaid estimated tax: the penalty and the safe harborsIndividuals owe less than: $1,000: no penalty; Current-year safe harbor: 90% of this year's tax; Prior-year safe harbor: 100% of last year's tax, 110% if AGI over $150,000; Penalty rate: Federal short-term rate plus 3 points, per late installment; Uneven income: Annualized income method on Form 2210; Corporations: Owe $500 or more; Form 2220.KEY FACTS AT A GLANCEUnderpaid estimated tax: the penalty and the safeharborsIndividuals owe less than$1,000: no penaltyCurrent-year safe harbor90% of this year's taxPrior-year safe harbor100% of last year's tax,110% if AGI over $150,000Penalty rateFederal short-term rateplus 3 points, per lateinstallmentUneven incomeAnnualized income methodon Form 2210CorporationsOwe $500 or more; Form2220Checked against official sourcesTax BakersUnderpaid estimated tax: the penalty and the safe harborsIndividuals owe less than: $1,000: no penalty; Current-year safe harbor: 90% of this year's tax; Prior-year safe harbor: 100% of last year's tax, 110% if AGI over $150,000; Penalty rate: Federal short-term rate plus 3 points, per late installment; Uneven income: Annualized income method on Form 2210; Corporations: Owe $500 or more; Form 2220.KEY FACTS AT A GLANCEUnderpaid estimated tax: thepenalty and the safe harborsIndividuals owe less than$1,000: no penaltyCurrent-year safe harbor90% of this year's taxPrior-year safe harbor100% of last year's tax, 110% if AGI over$150,000Penalty rateFederal short-term rate plus 3 points, perlate installmentUneven incomeAnnualized income method on Form 2210CorporationsOwe $500 or more; Form 2220Checked against official sourcesTax Bakers
Key facts at a glance, as set out in this guide.

How does the penalty work?

The tax is due as you earn income, through withholding or four estimated payments. If a payment is short or late, the penalty is calculated like interest on the shortfall, at the IRS underpayment rate, for the time it was outstanding. It is worked out separately for each installment, so paying more later in the year does not cancel an earlier shortfall. See estimated quarterly taxes.

What are the safe harbors for individuals?

Safe harborHow it works
Small balanceYou owe less than $1,000 after withholding and credits
Current yearYou paid at least 90% of this year's tax, in timely installments
Prior yearYou paid at least 100% of last year's tax, or 110% if last year's adjusted gross income was over $150,000 ($75,000 married filing separately)
No tax last yearYou were a US citizen or resident for the whole of last year and owed no tax

The prior-year safe harbor is the most useful for growing businesses, because it is known at the start of the year. See how much to set aside.

Why does withholding help?

Tax withheld from wages is treated as paid evenly through the year, unless you choose otherwise, even if it was withheld in December. Owners with a job, or S corporation owners on payroll, can increase withholding late in the year to cover a shortfall. See side hustle taxes.

What if income is uneven?

If most of your income arrives late in the year, the annualized income installment method on Form 2210 matches the required payments to when income was actually earned, which can reduce or remove the penalty.

When is the penalty waived?

  • A casualty, disaster or other unusual circumstance made paying inequitable.
  • You retired after reaching 62, or became disabled, in the year or the year before, and the underpayment was due to reasonable cause.

First-time abatement does not apply to this penalty. See first-time penalty abatement.

How does it work for corporations?

A C corporation expecting to owe $500 or more pays estimates in four installments. It avoids the penalty by paying 100% of this year's tax or, if it had a full 12-month year with tax due, 100% of last year's. Large corporations have restrictions on the prior-year method. The penalty is calculated on Form 2220. See Form 1120.

Want your estimates set to the safe harbor?

We work out payments that meet the safe harbor, and check the penalty calculation if a notice arrives.

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Questions people ask

What is the safe harbor for estimated tax?

Paying at least 90% of this year's tax, or 100% of last year's tax, or 110% if last year's AGI was over $150,000.

Do I owe an underpayment penalty if I owe less than $1,000?

No. Individuals who owe less than $1,000 after withholding and credits are not penalized.

Can first-time abatement remove the estimated tax penalty?

No. The estimated tax penalty is not covered by first-time abatement.

What if my income came mostly at the end of the year?

The annualized income installment method on Form 2210 can reduce or remove the penalty.

Sources

Every fee, date and rule on this page was taken from these official and primary sources.

  1. IRS: Underpayment of estimated tax by individuals penalty
  2. IRS: Form 2210, Underpayment of Estimated Tax by Individuals
  3. IRS: Form 2220, Underpayment of Estimated Tax by Corporations
  4. IRS: Estimated taxes

Rules and fees change. If you are reading this long after September 30, 2026, confirm the figures with the source before you rely on them.

Business tax by entity typeEstimated quarterly taxes: who pays and how to work them outFederal tax formsForm 1040-ES: paying estimated taxFreelancers and self-employedHow much to set aside for taxes when you're self-employed

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This guide is general information. It is not tax or legal advice for your situation.