Calculate your estimated tax underpayment penalty under IRC § 6654. Enter prior year tax and quarterly payments — see your safe harbor, underpayment per quarter, and penalty at ~8%/yr.
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| Quarter | Required | Paid | Underpaid | Penalty (~8%/yr) |
|---|
The Quarterly Tax Estimator calculates your exact safe harbor payments — so you never underpay again.
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The IRS requires self-employed individuals, freelancers, and investors to prepay their taxes throughout the year via quarterly estimated payments. If you skip or underpay these installments and owe $1,000 or more at filing, the IRS charges an underpayment penalty under IRC § 6654 — even if you pay your full tax bill on April 15.
The penalty rate equals the IRS short-term Applicable Federal Rate (AFR) plus 3 percentage points, compounded daily. For 2026, this works out to approximately 8% per year. Each quarter is calculated separately — an underpaid Q1 accrues penalty from April 15, 2026 all the way to April 15, 2027 (365 days), while a missed Q4 installment (due January 15, 2027) only accrues for ~90 days to the April 15 filing deadline.
| Safe harbor (100% of $11,525) | $11,525.00 |
| Required per quarter (÷ 4) | $2,881.25 |
| Total paid (missed all quarters) | $0.00 |
| Q1 underpayment ($2,881 × 8% × 365/365) | $230.50 |
| Q2 underpayment ($2,881 × 8% × 303/365) | $190.95 |
| Q3 underpayment ($2,881 × 8% × 212/365) | $133.70 |
| Q4 underpayment ($2,881 × 8% × 90/365) | $56.79 |
| Total estimated penalty | $611.94 |
Note: The $922 penalty figure cited by competitors assumes a different underpayment amount or prior year tax. Your actual penalty depends on your specific prior year tax, AGI, quarterly payments, and the current AFR. Use the calculator above for your exact numbers.
The IRS gives you two ways to avoid the penalty entirely — you only need to satisfy one:
Safe Harbor 1: Prior Year Tax. Pay at least 100% of your previous year's total tax (Form 1040, line 24) in equal quarterly installments. If your prior year AGI exceeded $150,000, the threshold rises to 110%. This is the most common method because you know the exact number — it's right on last year's return.
Safe Harbor 2: 90% of Current Year Tax. Pay at least 90% of your actual current-year tax liability. This is harder to use mid-year because you don't know your final tax until year-end. It's most useful for people whose income dropped significantly from the prior year — if you're paying 100% of last year's higher tax when this year's income is 30% lower, the 90% method might let you pay less.
The safest approach for most self-employed people: use the prior year method. Look at your prior year line 24, divide by 4, pay each installment on time. You're completely protected from the penalty regardless of what your income does this year.
Form 2210 is the IRS worksheet for calculating the underpayment penalty and documenting exceptions. You file it with your Form 1040. You may voluntarily attach Form 2210 to:
• Self-calculate a lower penalty than the IRS would assess (especially useful if your income was uneven across quarters — the annualized income installment method on Schedule AI can reduce your penalty significantly if you earned most of your income in Q3 or Q4)
• Claim an exception — the penalty is waived if: (a) your total underpayment was less than $1,000, (b) you had no tax liability in the prior year (tax year was 12 months), (c) you retired or became disabled and the underpayment was due to reasonable cause, or (d) a federally declared disaster applies
If you don't attach Form 2210, the IRS will calculate and bill the penalty based on their records. If you owe the full penalty with no exceptions, you can let the IRS calculate it — just pay when billed. If you think you qualify for a lower amount, file Form 2210.