Estimated Tax Underpayment Penalty Calculator (Form 2210)

How to do it

1. 1
   Enter this year's tax and last year's tax

   Use your estimated tax after credits for this year and the total tax from last year's return.

2. 2
   Enter your income

   Your last-year adjusted gross income decides the 100 or 110 percent safe harbor.

3. 3
   Enter payments by installment

   Type what you paid on each of the four due dates.

4. 4
   Add withholding

   Enter total withholding for the year; it is spread over the four installments.

5. 5
   Read the penalty

   See the required payment, the shortfall for each installment and the estimated penalty.

About this tool

If too little tax is paid during the year, through withholding or estimated payments, the IRS charges a penalty that works like interest. You can avoid it by paying at least 90 percent of this year's tax or 100 percent of last year's tax (110 percent if your income was above $150,000). This calculator checks those safe harbors, splits the required amount into four installments, compares them with what you paid on each due date and estimates the penalty with the quarterly interest rates in an editable table.

Who this is for Freelancers, landlords, investors and employees with side income who make estimated payments, and anyone surprised by a large tax bill at the end of the year. It helps you see, in October or December, whether a catch-up payment would reduce the penalty.

The safe harbors You owe no penalty if your total tax after credits is less than $1,000 after subtracting withholding. Otherwise the required annual payment is the smaller of 90 percent of the current year's tax or 100 percent of the prior year's tax, 110 percent if the prior year's adjusted gross income was above $150,000. The required annual payment is divided into four installments due on April 15, June 15, September 15 and January 15 of the next year.

How the penalty is estimated For each installment the tool compares the cumulative amount required with the cumulative amount paid. If the payments fall short, the shortfall accrues interest from the due date until the next due date and then until the filing date, using the IRS rate in effect for each quarter, 7 percent in most quarters of 2026 and 6 percent in the second quarter. Withholding is treated as paid in four equal parts, which is the IRS default and often helps people who increased their withholding late in the year.

Worked example Current-year tax is $18,000 and last year's tax was $14,000, with income below $150,000. The safe harbor is the smaller of $16,200 and $14,000, so the required annual payment is $14,000 and each installment is $3,500. If $2,500 was paid at each date, the shortfall grows from $1,000 to $4,000, and the penalty comes out at a few hundred dollars. Paying $3,500 on each date removes it.

Limits Farmers and fishermen, annualized income and uneven income have their own rules in Form 2210, and the actual penalty is calculated by the IRS or your software. This tool gives an estimate for planning, not tax advice.

Worked example

With current tax of $18,000, prior-year tax of $14,000 and $2,500 paid at each due date, the required payment is $14,000, each installment is $3,500 and the estimated penalty is a few hundred dollars.