About TaxSums
12 UK tax calculators, built to be correct and kept correct through every Budget.
Why this site exists
Most UK tax calculators give you a number and nothing else. You cannot see which bands were used, where the rates came from, when they were last checked, or what the tool cannot handle. When the number disagrees with your payslip, you have no way to find out which is wrong.
Worse, a lot of them are quietly inaccurate. Common errors we found while researching this site: treating all three pension arrangements as identical, applying a single Capital Gains Tax rate to a gain that straddles two, claiming the Employment Allowance for one-person companies that cannot have it, and using the wrong boundary for the additional rate band. Each is invisible unless you already know the answer.
We built this to do the opposite:
- Show the working. Every result comes with the band table behind it.
- Cite the source. Every rate links to the HMRC or devolved authority page it came from, with the date we last checked it.
- State the limits. Where a calculation cannot capture your situation, the page says so.
Who writes this
TaxSums is written and maintained by the TaxSums editorial team. We are not accountants and we do not offer advice — we build tools and explain the rules behind them, working from primary sources.
What we do have is a disciplined process: every rate held in one versioned, sourced data file; a calculation engine covered by 112 unit tests built from HMRC worked examples; and results cross-checked against established calculators before launch, with any disagreement investigated rather than assumed away. Read the methodology.
How it stays current
The hard part of a tax calculator is not building it — it is keeping it right. Rates change at every Budget, and abandoned calculators do not announce that they are out of date.
Our rates live in a single data file per tax year, typed against a schema that will not compile if a figure is missing. Updating for a Budget is a data change, not a hunt through calculator code. We review after each Budget and Spring Statement, and again each April. The changelog records every change with its date.
Current figures are for the 2026/27 tax year, reflecting the Autumn Budget of 26 November 2025, verified on 7 August 2026.
How this is funded
By advertising. The calculators are free, there is no account to create, no email to hand over, and nothing is behind a paywall. We do not sell data — we do not collect any.
Ads are kept away from the inputs and results so they cannot be tapped by mistake or confused with the calculation. If that ever stops being true, we have got the balance wrong and would rather hear about it.
Your privacy
Every calculation runs in your browser. Salary, property price, redundancy package — none of it is sent to us or stored anywhere. There is no account, and no server ever sees what you type. Full privacy policy.
Corrections and suggestions
If a figure looks wrong, please tell us — send the inputs you used and what you expected. Corrections are the most valuable thing anyone sends us and they are fixed the same day. Suggestions for calculators we should build next are welcome too.
TaxSums provides information, not financial or tax advice. Our calculators are estimates to help you understand your position and ask better questions. Check anything important with a qualified accountant or with HMRC before acting on it.