This self-employed estimated tax calculator works out a safe-harbor figure from your prior-year return and splits it across the four payment periods. Runs in your browser. Nothing is stored or sent anywhere.
Estimated Tax Safe-Harbor Calculator
Planning estimate based on the prior-year safe harbor, not tax advice. Confirm with a CPA.
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One operating decision, worked through with numbers
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Why this self-employed estimated tax calculator uses last year’s tax
There are two broad ways to size an estimated tax payment. You can project the current year’s income and pay against that projection, or you can pay against what you already owed last year.
For a seller whose revenue moves month to month, the second approach is usually the more stable one to plan around. Last year’s tax is a number that already exists on a filed return. This year’s income is a guess that changes every time a month closes, and a guess that comes in low can leave a shortfall spread across periods that have already passed.
That is what a safe harbor is for: a known figure that can keep an underpayment penalty from applying even when the year turns out better than expected. The specific percentages and the income level at which they change are set by the IRS — the official rules live in Estimated Taxes on IRS.gov — and are laid out with the method in the full guide below.
What you need before you start
- Your prior-year total tax. This is the total tax line on last year’s federal return, not the balance you paid in April and not your refund.
- Your prior-year adjusted gross income. The safe-harbor percentage can change above a certain AGI, so the calculator asks for it.
One thing the calculator does not net out: withholding. If you or a spouse has W-2 withholding, it counts toward the same annual obligation. Subtract the withholding you expect for the year from the safe-harbor target before you divide what is left across the remaining payment periods. A household with substantial W-2 withholding can owe far less in quarterly payments than the raw target suggests, and occasionally nothing at all.
The part operators most often get wrong
Estimated tax periods are not calendar quarters. The four periods are uneven, and the due dates do not sit three months apart. A seller who mentally divides the year into four equal blocks tends to be late on the period that is shorter than it looks.
The second common miss is treating the 1099-K figure as the income to pay tax on. It is not. A 1099-K reports gross payments processed before refunds, fees, chargebacks, shipping collected, and sales tax collected come out. Paying estimated tax against that gross number generally means overpaying, sometimes substantially.
What this does not do
- It does not calculate your actual tax. It sizes a payment against a prior-year figure. Your real liability is settled on the return.
- It does not cover state estimated tax. States set their own rules, thresholds, and dates.
- It does not handle the annualized income method, which can suit a seller whose income is concentrated in one part of the year and may be worth reviewing with a CPA.
Related
- Do You Have to Pay Quarterly Taxes on Shopify Income? — the full method, the current safe-harbor percentages, and the payment periods
- Does Shopify Send You a 1099-K? — why the 1099-K figure is not the income to pay tax on
- All free calculators
Frequently asked questions
How do self-employed sellers calculate estimated taxes?
Two routes are common: project current-year income and pay against the projection, or pay a safe-harbor amount based on the prior-year return. This calculator uses the second, because it works from a figure that is already fixed rather than one that moves all year.
Do I owe estimated tax if my store lost money this year?
Possibly not, but a safe-harbor calculation is based on last year’s tax rather than this year’s result, so a loss year does not automatically remove the obligation. This is a good case to confirm with a CPA before skipping payments.
Does the 1099-K amount tell me what to pay?
No. The 1099-K reports gross payments before refunds, processing fees, chargebacks, shipping collected, and sales tax collected are removed. Taxable income sits below that figure.
Are my numbers saved anywhere?
No. The calculator runs entirely in your browser. Your inputs stay on your device and are remembered locally only so the figures are still there next visit.