About Estimate My Tax
Estimate My Tax is a free, independent calculator for working out roughly how much Income Tax and National Insurance a self-employed person owes under UK Self Assessment. It was built because the gap between "I earned this" and "I owe this" is wider than it should be, and most people only find out the number when the bill lands.
What we are
We're an independent tool, not a tax authority and not an accountancy firm. The calculator uses the published tax bands, allowances and National Insurance rates for each supported year (2022-23 through 2025-26) and shows the working in the same order HMRC's own calculation follows, so the output is easy to check against a real tax calculation.
What we are not
We are not HMRC and we are not affiliated with GOV.UK. We don't produce official documents, we can't see your tax record, and we can't file anything on your behalf. An estimate from this site is not an official SA302 and should not be sent to a mortgage lender in place of one. When money or a mortgage depends on the exact figure, use the real calculation from HMRC or ask a qualified accountant.
Why it's free
The calculator is free to use and always will be. It costs almost nothing to run: the site is plain static files, and the maths happens on your own device rather than on a server we have to pay for. We intend to carry advertising to cover the hosting, and this page will say so plainly once ads actually appear.
What the model rules out matters more than what it funds. We never need your email address, an account, or any financial detail stored anywhere. There is nothing to sell, because we don't collect it.
Accuracy
The engine is tested against real HMRC tax calculations, and it reproduces them to the penny. We've published every check figure, the profile behind it and the limits of what's been verified on the methodology page, so you can judge the accuracy yourself rather than take our word for it.
Tax is full of edge cases. Scottish and Welsh rates, Marriage Allowance, student loan repayments, Gift Aid, capital gains and the High Income Child Benefit Charge are all outside what this estimator covers today, and the methodology page lists them explicitly. If you spot something that looks wrong, please tell us — corrections are the most useful message we get.