Self-employed and 1099 income means the IRS wants its cut four times a year, not once. Miss the safe-harbor rule and you owe a penalty on top of the tax. This interactive tool, built by a licensed CPA, runs the real 2026 numbers and tells you what to send in, and when.

What it calculates: your quarterly payment using the safe-harbor rule (100%/110% of last year’s tax), your income tax and self-employment tax combined, all four 2026 due dates with the exact amount for each, and what the underpayment penalty looks like if you skip a quarter.

Perfect for freelancers, 1099 contractors, and small business owners paying estimated taxes for the first time, or tired of guessing.

Download, open in any browser (desktop, tablet, or phone, no software or login), enter your numbers, and get your four payment amounts and dates.

Built by Sophia Sinclair Miller, CPA. Estimates 2026 federal tax for planning only. Not tax advice; no CPA-client relationship created.