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Quarterly estimated tax calculator (2026)
If you take profit from an LLC or work for yourself, nobody withholds tax for you. The IRS expects four payments through the year and charges interest when they fall short. This gives you a working number for each date.
- Built by a team of Certified Accountants, CPAs and Enrolled Agents
- 2026 figures
- Estimate only, not advice
Estimate only. Uses 2026 federal brackets, the 2026 standard deduction ($16,100 single, $32,200 joint), self-employment tax at 15.3% on 92.35% of profit up to the $184,500 Social Security wage base and 2.9% above it, the deduction for half of self-employment tax, and a simplified 20% qualified business income deduction. Credits, dependants, itemised deductions and phase-outs are ignored.
Who has to pay estimates
Anyone who expects to owe $1,000 or more in federal tax for the year after withholding and credits. For a sole proprietor, a single-member LLC owner, a partner or an S-corp owner taking distributions, that is almost everyone with a profitable business, because nobody withholds tax from business income. The payments are due April 15, June 15 and September 15 of the tax year and January 15 of the following year. Miss or underpay one and the IRS charges an underpayment penalty that works like interest, currently around 7% a year, from that quarter's date.
The two taxes hiding in one number
Self-employment tax is the one people forget. It is Social Security and Medicare for people who are their own employer: 15.3% on 92.35% of net profit, up to the Social Security wage base of $184,500 in 2026, then 2.9% for Medicare above it. It applies before any deduction or credit, which is why a business that shows a small profit after expenses can still owe several thousand dollars.
Income tax then applies to profit plus any other income, after the standard deduction ($16,100 single, $32,200 joint in 2026), half of the self-employment tax, and the 20% qualified business income deduction most small business owners qualify for. The calculator applies all three in that order.
Safe harbour: the rule that removes the guesswork
You will not be penalised if your four payments add up to at least 100% of last year's total tax (110% if last year's adjusted gross income was over $150,000), paid in equal instalments, even if this year turns out much better. Owners with growing profits use the safe harbour deliberately: pay last year's number in four parts, keep the difference in the bank, and settle up on April 15. Owners with falling profits should calculate instead, because the safe harbour overpays.
S-corp owners have a third option
An S-corp pays its owner a salary through payroll, and payroll withholding counts as if it were paid evenly through the year. Owners who set withholding on the December salary high enough can cover the year's tax without making estimates at all. It is a legitimate timing advantage and one of the smaller reasons S-corps appeal to owners with irregular income.
State estimates
Most states with an income tax also expect quarterly payments, on the same dates or close to them, with their own safe-harbour rules. The calculator lets you add a flat state rate; your state page has the actual rate and the agency link.
Questions people ask
What happens if I skip the estimates and pay everything in April?
You pay the full tax plus an underpayment penalty calculated per quarter, at roughly 7% a year on the shortfall. On $20,000 of tax paid a year late that is around $700. Not catastrophic, but avoidable.
Do I have to pay four equal amounts?
The safe harbour assumes equal instalments. If income is uneven, the annualised income method lets you pay less in slow quarters, but it requires a schedule with the return (Form 2210).
My spouse has a W-2 job. Can their withholding cover my business?
Yes, on a joint return all withholding counts toward the household total. Increasing a spouse's withholding is often simpler than four separate payments.
How do I actually pay?
IRS Direct Pay or an IRS online account, choosing "estimated tax" and the 2026 tax year, or by mailing a 1040-ES voucher. Keep the confirmation numbers; they are asked for when the return is prepared.
Does the calculator include the additional Medicare tax?
No. The 0.9% additional Medicare tax applies above $200,000 (single) or $250,000 (joint) of combined wages and self-employment income; add it if you are above those levels.
Will you calculate this for me each quarter?
Yes. Quarterly tax planning is part of the Growth and Enterprise bookkeeping plans and of every virtual CFO engagement, and we can do it standalone from the books you already have.
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