Calculator
Quarterly Estimated Tax
Nobody withholds anything from a 1099, so the whole bill has to be estimated and paid in voluntarily. This runs the full chain — self-employment tax on 92.35% of profit, the deduction for half of it, the 20% qualified business income deduction, then income tax — and gives you both numbers that matter: what you'll actually owe, and the smaller safe-harbor amount that keeps the penalty away.
Uses published 2026 federal figures
What to send in · 2026
Enter your net profit for the year, then press Calculate to see what to send in and when.
Your business
Net profit is gross receipts less business expenses — the bottom line of Schedule C, before any personal deductions. Don't subtract your health premiums or retirement contributions here; those go in their own boxes and are deducted further down the chain.
The QBI deduction is 20% of qualified business income, capped by 20% of taxable income excluding capital gains. Most Schedule C filers qualify. Leave it on unless you know your line of work is excluded at your income level.
Gross receipts less business expenses, for the whole year
Most Schedule C filers qualify. Turn it off if your line of work is a specified service business and your income is past the phase-out — the phase-out itself isn't modeled here.
The rest of your year
W-2 wages matter for more than income tax: they use up the Social Security wage base first, so $184,500 of wages means the 12.4% stops applying to your profit entirely. Include a spouse's wages on a joint return.
Any tax withheld from those wages counts toward the same requirement your estimated payments do — and unlike a quarterly payment, withholding is treated as paid evenly across the year no matter when it happened.
Deduction
HSA, student loan interest, and so on
Where you are in the year
Estimated tax is paid in four installments, due April 15, June 15, September 15, and January 15. Whatever is left of the year's requirement is split across the installments still ahead of you — so a late start means bigger payments, not a smaller total.
Payments already made are your own estimated payments so far. They count toward the requirement alongside any withholding.
Your own quarterly payments so far this year
A flat estimate, applied to profit and investment income
Last year, for the safe harbor
You avoid the underpayment penalty by paying in the smaller of 90% of this year's tax and 100% of last year's — 110% if last year's AGI was over $150,000.
In a growing year the prior-year figure is usually far cheaper, and paying it rather than the full bill is a legitimate, interest-free choice: the rest is settled at filing with no penalty. Both figures are on your prior return, at line 24 and line 11.
Form 1040, line 24
Form 1040, line 11
Leave both at zero and only the 90%-of-this-year test is used, which is the stricter assumption — you will never be told to pay in less than you actually need to because a figure was missing.
For educational purposes only. Results are estimates and do not constitute financial, tax, or legal advice. Consult a qualified professional before making any financial decisions.
How to use it
Start with your best estimate of net profit for the whole year — gross receipts less business expenses. Don't subtract health premiums or retirement contributions there; those have their own boxes and are deducted at a later step in the chain.
Fill in last year's tax and AGI if you have your prior return to hand. In a growing year they usually make the safe harbor far cheaper than 90% of the current bill, and leaving them blank means the tool assumes the stricter test.
Set installments still ahead to where you are in the calendar. Starting late doesn't reduce the total — it packs it into fewer payments, which the schedule shows plainly.
Press Example to load a worked case: a freelancer clearing $95,000 with their own health cover and a solo 401(k).
Two numbers, not one
What you will owe is the real bill for the year. The safe harbor is the smaller amount you have to pay in through the year to avoid an underpayment penalty — the lesser of 90% of this year's tax and 100% of last year's, or 110% if last year's AGI was over $150,000.
Paying the safe harbor rather than the full bill is a legitimate choice, not a mistake: the Treasury charges you nothing for the difference until filing. In a year when income jumps, it can leave a lot of money in your account for an extra twelve months.
The catch is that the difference is still owed in April. That is the number people are surprised by, so it gets its own line rather than being left for the reader to subtract.
Why self-employment tax bites first
An employee splits Social Security and Medicare with their employer. A self-employed person pays both halves — 15.3% on 92.35% of profit, which works out to about 14.1% of the profit itself.
It does not care about the standard deduction. Someone clearing $12,000 pays no income tax at all and still owes around $1,700 of self-employment tax, which is the single most common first-year surprise.
At moderate profits it is usually the larger of the two taxes, which is why the breakdown chart is on the results rather than buried in the working. If you also have a job, its wages use up the Social Security wage base first, and the tool accounts for that.
Assumptions and limits
- Brackets, the standard deduction, and the Social Security wage base are the published 2026 figures. They change every year.
- The QBI deduction is 20% of profit less half the self-employment tax, health premiums, and retirement contributions — capped at 20% of taxable income excluding capital gains. The specified-service phase-outs are not modeled, so turn the toggle off if they apply to you.
- The requirement is split evenly across the installments still ahead. The IRS also allows an annualized-income method for uneven earnings, which can lower an early payment; that isn't modeled.
- Withholding counts as paid evenly across the year regardless of when it happened, which is why raising it late in the year can fix an underpayment a quarterly payment can't.
- State tax is one flat rate you supply, applied to profit and investment income but not to wages. State due dates don't always match the federal ones.
- Not modeled: the alternative minimum tax, tax credits, business losses carried forward, partnership or S-corp income, or household employment tax.
- An estimate for planning. Not tax advice, and not a substitute for someone looking at your actual return.