Paid script
2026 Quarterly Estimated Tax Helper for the Self-Employed
Find out roughly what you owe in 2026 and how much to pay each quarter to avoid an underpayment penalty, explained in plain English. It works from a single year-to-date number or from a CSV of your income and expenses.
Paid script
Quarterly Estimated Tax Helper
Buy this script on its own for $29, one time. No membership needed. It runs on your own computer and nothing you enter leaves it. Read how it works and the questions below first.
The Automation Suite includes this and 10 more tools for $99. Members get this included. See the membership or sign in. Already bought it? Email me my access link.
How it works
How it works
Enter your year-to-date net self-employment profit, or point the script to a CSV of income and expenses, along with your filing status, any wages and withholding, and last year's tax. The script projects your full-year profit and computes 2026 self-employment tax: 15.3% on 92.35% of profit, with social security capped at the $184,500 wage base, plus the 0.9% Additional Medicare Tax above the threshold. It then subtracts half of the SE tax and the 2026 standard deduction and applies the 2026 tax brackets to estimate federal income tax. Next it works out the safe-harbor payment, which is 90% of this year's tax or 100% of last year's (110% if last year's AGI was over $150,000). Finally it lays out the April 15, June 15 and September 15, 2026 and January 15, 2027 payments, credits what you have already paid and adds a catch-up line for any missed quarter.
FAQ
About this calculator
What do I need to run it?
Python 3.9 or newer. You can type your year-to-date profit on the command line or use a CSV of income and expenses. It uses only the standard library and works offline. Try --demo first.
Does it include New Jersey estimated tax?
No. It covers federal tax only. New Jersey residents usually make separate NJ estimated payments, so check the NJ Division of Taxation or ask your preparer.
What does it leave out?
It leaves out the QBI deduction, the senior, tip and overtime deductions, retirement contributions, self-employed health insurance and credits unless you enter them with the matching options. Leaving these out usually makes the estimate on the high side.
Is this tax advice?
No. It is a planning estimate based on the numbers you enter and the published 2026 IRS rates. Your actual tax is figured on your return, so confirm with a tax professional.
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