How much is the penalty?

It's figured like interest: the IRS underpayment rate (the federal short-term rate plus 3%) on each shortfall, for the days it's outstanding. The rate changes every quarter, so this calculator shows the shortfalls and dates rather than guessing the dollar amount.

Does paying early help?

Yes. Anything you pay ahead carries forward and counts toward the next installment.

What if my income came late in the year?

Use the annualized income installment method on Form 2210 (Schedule AI). It figures each installment from what you'd actually earned by then, so a big December doesn't create penalties back in April.

Where do I send the payments?

IRS Direct Pay or EFTPS are the easy ways, or through your IRS online account. Keep the confirmation numbers.

TaxesTax years 2025 & 2026

Quarterly Estimated Tax Calculator

Check your estimated payments quarter by quarter, the way Form 2210 does: what was due by each date, where you came up short, and what it takes to catch up.

Ben / Reviewed Sep 27, 2026 / v2.0.0

Your numbers

Tax year

Filing status

Last year

Last year's tax

Last year's AGI

Did last year's return cover the full year?

This year

This year's tax (your best guess)

Federal withholding for the whole year

Estimated payments

What you've paid so far, plus what you plan to pay. Leave future ones at $0 to see what catching up takes.

Q1 (April)

Q2 (June)

Q3 (September)

Q4 (January)

Results

Showing the numbers you calculated

Heads up

Q2: $2,250.00 short on 06/15/2026, caught up by the 09/15/2026 payment. Expect a small penalty on that amount for the days in between.

Due each quarter: $6,250.00; 25% of the $25,000.00 safe harbor (last year's tax)
Installments short: 1; Each one carries a penalty for the days it was short
Paid in total: $25,000.00; Withholding + estimated payments
Left to pay when you file: $5,000.00; The safe harbor avoids the penalty, not the tax

Quarter by quarter

Running totals, the way Form 2210 figures it: withholding counts evenly, and later payments cover earlier shortfalls first.

Swipe the table sideways to see all 7 columns.

Quarter by quarter
Installment	Due	Required to date	Paid to date	Status	Short by	To be caught up, pay
Q1	04/15/2026	$6,250.00	$6,250.00	On track	$0.00	$4,250.00
Q2	06/15/2026	$12,500.00	$10,250.00	Short	$2,250.00	$4,250.00
Q3	09/15/2026	$18,750.00	$18,750.00	On track	$0.00	$6,500.00
Q4	01/15/2027	$25,000.00	$25,000.00	On track	$0.00	$4,250.00

What this does

Estimated taxes aren't one annual bill split four ways. Each quarter is its own deadline, and the underpayment penalty is figured quarter by quarter — so paying everything in January still costs you for the months you were behind.

Put in what you've paid (and what you plan to pay), and this checks each installment the way Form 2210 does: what was due by that date, what you'd paid, where you were short, and when a later payment caught you up.

How the math works

First the target — the safe harbor, the same as the Safe Harbor calculator:

safe harbor = the smaller of 90% of this year's tax or 100% of last year's (110% if last year's AGI was over $150,000)

Then 25% of it is due by each installment date. The calculator keeps running totals:

required to date = 25% × the installments so far
paid to date = withholding (counted evenly) + the estimated payments so far
short = required to date − paid to date, when that's positive

A later payment covers the earliest shortfall first, and anything extra carries forward. That's why a quarter can be short and the next one fine.

Withholding counts as paid evenly across all four quarters, even if it came out in December. If you're short and have a W-2 job, raising your withholding fixes the earlier quarters too.

Check my math: a worked example

This year's tax looks like $30,000, last year's was $25,000, and $8,000 is withheld from a paycheck. Estimated payments: $4,250, $2,000, $6,500, $4,250.

Safe harbor: $25,000.00 (last year's tax), so $6,250.00 is due by each installment. Withholding covers $2,000.00 of every one.
Q1 (04/15/2026): $6,250.00 required so far, $6,250.00 paid — right on target.
Q2 (06/15/2026): $12,500.00 required so far, $10,250.00 paid — short $2,250.00.
Q3 (09/15/2026): $18,750.00 required so far, $18,750.00 paid — right on target.
Q4 (01/15/2027): $25,000.00 required so far, $25,000.00 paid — right on target.
The shortfall was caught up later, so the penalty is only for the days in between — small, but not zero.
You'd still owe $5,000.00 when you file.

These numbers come straight from the calculator using its example inputs — if the math ever changes, this example changes with it.

Mistakes I see a lot

Treating the four payments as one annual bill. A catch-up in January doesn't erase a short June.
Using this year's AGI for the 110% test — it's last year's.
Listing a late payment under the quarter it was meant for. It counts when you actually paid it.
Forgetting that a refund applied from last year counts as a Q1 payment.
Ignoring the annualized method when most of your income came late in the year. It can shrink or erase early penalties (Form 2210, Schedule AI).

Questions people ask

How much is the penalty?: It's figured like interest: the IRS underpayment rate (the federal short-term rate plus 3%) on each shortfall, for the days it's outstanding. The rate changes every quarter, so this calculator shows the shortfalls and dates rather than guessing the dollar amount.
Does paying early help?: Yes. Anything you pay ahead carries forward and counts toward the next installment.
What if my income came late in the year?: Use the annualized income installment method on Form 2210 (Schedule AI). It figures each installment from what you'd actually earned by then, so a big December doesn't create penalties back in April.
Where do I send the payments?: IRS Direct Pay or EFTPS are the easy ways, or through your IRS online account. Keep the confirmation numbers.

Assumptions and limits

Federal only (IRC §6654). States have their own rules.
The safe harbor is the lesser of 90% of this year's tax or 100% of last year's — 110% if last year's AGI was over $150,000 ($75,000 married filing separately). No penalty if you owed no tax last year, or if this year's tax minus withholding is under $1,000.
Regular installment method (Form 2210, Part III): 25% of the safe harbor is due by each installment date.
Withholding counts as paid evenly on the four due dates. Each estimated payment counts on the due date of the installment you list it under.
Payments go to the earliest shortfall first, and anything extra carries forward to the next installment.
The penalty itself isn't calculated: it's the IRS underpayment rate on each shortfall for the days it's outstanding, and the rate changes every quarter.
The annualized income installment method (Schedule AI), farmer and fisherman rules, and fiscal years aren't covered.

Ben’s notes on this

Related calculators

Estimated Tax Safe Harbor
The least you can pay in estimated taxes and still owe no underpayment penalty — which rule you're under, what's left after withholding, and what to send each quarter.
Self-Employment Tax
The Social Security and Medicare tax you pay as your own boss, figured line by line like Schedule SE — including a W-2 job's effect on the wage base, the Additional Medicare Tax, and how much to set aside.
Salary to Contractor Rate
Leaving a salaried job to contract? The hourly rate that actually replaces your salary, benefits, and the payroll tax your employer used to pay — with unpaid time off and unbilled hours counted.

Spot an error?

This is a public notebook and I do make mistakes. If a number looks off, tell me — I fix things and note the change in the changelog.

Disclaimer: Educational and planning use only. Results depend on what you enter and may not match your lender, your tax return, or professional accounting treatment. Informational content + opinions only — not tax/legal advice. Tax rules change and have exceptions this calculator doesn't cover — confirm current rules and your specific facts before relying on the result.