Quarterly Estimated Tax & Safe Harbor Calculator
Enter your income and last year's numbers to see both safe-harbor targets side by side, plus your per-quarter payment amount and due dates for 2026.
Your safe-harbor targets
90% of this year's estimated tax
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100% of last year's tax
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Add last year's tax and AGI above to compare.
Your safe-harbor target (annual)
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Already covered
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Still owed
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Per quarter
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Quarterly payment vouchers
Q1
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Q2
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Q3
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Q4
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Did you already underpay?
Enter what you actually paid each quarter to estimate the underpayment penalty on any shortfall.
Estimated underpayment penalty
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Estimates for tax year 2026, for informational purposes only — not tax advice. Underpayment-penalty mechanics are simplified — this estimate applies each quarter's own IRS interest rate (7%/6%/7%/7% for 2026) as simple interest through the following April, rather than the exact daily-compounded, multi-rate-period calculation Form 2210 uses, and generally runs a bit higher than the real penalty. Consult a tax professional or IRS Form 2210 for your exact amount.
How the safe-harbor comparison works
The IRS lets you avoid an underpayment penalty by paying the lesser of two targets across the year: 90% of your current-year tax, or 100% of last year's tax. That second number rises to 110% if last year's AGI was over $150,000. This calculator computes both numbers from what you enter. It highlights the one that wins, instead of just showing you the final answer.
Worked example: a growing business
A single Texas freelancer earning $150,000 this year (up sharply from last year), who owed just $8,000 in total tax last year on a $45,000 AGI:
- 90% of this year's estimated tax: $33,847
- 100% of last year's tax: $8,000
- Winning target: $8,000 (the prior-year number — a known figure that's far lower than paying 90% of this year's much bigger tax bill)
- Per-quarter payment: $2,000
Worked example: a shrinking business
A single Texas freelancer earning $40,000 this year (down from a bigger year before), who owed $30,000 in total tax last year on a $180,000 AGI (above the high-income threshold, so the prior-year percentage rises to 110%):
- 90% of this year's estimated tax: $6,684
- 110% of last year's tax: $33,000
- Winning target: $6,684 (this year's own number — since income dropped, 90% of this year's smaller tax beats 110% of last year's bigger one)
- Per-quarter payment: $1,671
2026 due dates
- Q1: April 15, 2026
- Q2: June 15, 2026
- Q3: September 15, 2026
- Q4: January 15, 2027
Frequently asked questions
What's the difference between this and the main 1099 tax calculator?
The main calculator gives you a full income-tax breakdown with quarterly amounts as one part of the output. This tool puts the safe-harbor comparison front and center — it shows both the current-year and prior-year targets side by side so you can see exactly which one wins and why, which is useful if you already have a rough sense of your total tax and just need the payment schedule.
Which safe-harbor target should I plan around?
Whichever is lower — that's the whole point of the rule. A known prior-year number is easier to plan around than an estimate of a year that isn't over yet, so if your income is flat or growing, the prior-year target is usually both the lower and the safer choice.
What if I don't know my prior-year total tax or AGI?
You can find both on last year's Form 1040 — AGI is on line 11, and total tax is on line 22 (sometimes labeled differently by tax software, but that's the IRS form line). Without them, this tool falls back to 90% of this year's estimated tax as your only target.
Do these payments cover my state's estimated tax too?
No — the safe-harbor calculation here is a federal rule (IRC §6654). Most states with an income tax have their own separate estimated-payment requirements and forms; check your state department of revenue for its own quarterly rules.
How much is the underpayment penalty?
It's simple interest on each quarter's shortfall, charged at the IRS's current underpayment rate (7% for most of 2026, dipping to 6% for Q2) from that quarter's due date until you catch up or file. Enter what you actually paid each quarter in the "Did you already underpay?" section above for an estimate — the real Form 2210 calculation compounds daily across multiple rate periods, so your actual penalty is usually a bit lower than this estimate.