About this site
Twenty-six free calculators and thirty-eight plain-English guides covering UK small business tax, payroll, VAT, company filings and the construction trades. No signup, no email wall, and every figure dated and linked to the source it came from.
Updated 14 September 2026
Why it exists #
Most tax calculators online go wrong in the same two ways. They take a single figure and apply a flat percentage to it, ignoring the thresholds, tapers and reliefs that decide the real answer. And they do not say which tax year they are using, so a page written three years ago looks exactly like one updated last week.
The CIS calculator is the clearest example. Most of them multiply the whole invoice by 20%. That is wrong on any job involving materials, because CIS is deducted from labour only. On a £2,500 invoice with £500 of materials the correct deduction is £400, not £500 — a £100 error on one invoice, repeated every month.
The same pattern runs through the rest. A salary sacrifice calculator that ignores the benefit in kind charge on the car. A business rates page still quoting multipliers from before the 2026 revaluation. A redundancy calculator that misses the cap on a week's pay. Every tool here shows its full working, so you can see which figure drove the answer instead of trusting a single number.
How the figures are checked #
Every rate, threshold and deadline is held in one place, and each carries two things with it: the date it was last checked, and a link to the HMRC or GOV.UK page it came from. Both appear at the foot of each page, so any figure can be verified without taking it on trust.
- Nothing is copied from another site. Figures come from the primary source, normally HMRC, GOV.UK, Companies House or the legislation itself
- Unexpected movements are cross-checked. A fee that falls, or a rate that drops, is confirmed against a second official source before it is published
- Official guidance is not assumed to be current. Where HMRC's own helpsheets still show a superseded rate, the page says so rather than repeating it
- Calculations are tested against published worked examples, at the boundaries as well as in the middle, because that is where rounding and tapers break
The editorial policy sets out how pages are written and reviewed in more detail.
When it gets something wrong #
It will, eventually. Rates change mid-year, guidance gets reinterpreted, and a figure that was right in April can be wrong by November. When an error is found it is corrected and logged publicly on the corrections page, showing what was wrong, what it is now, and when it changed. Corrections are not quietly edited away.
If you have found a mistake, or a rate that has moved, get in touch. Corrections are the most useful thing anyone sends.
Who publishes it #
Business Taxation is an independent UK publisher. It is not owned by, funded by or affiliated with any accountancy firm, software vendor, umbrella company or accreditation body, and it does not sell accountancy services. Nobody pays to appear in a comparison or to be described favourably in a guide.
What this site is not #
It is not tax advice for your situation, and it is not a substitute for an accountant. The calculators produce estimates to help you plan, to check a figure someone else has given you, and to understand which rules are driving it. For advice on your own circumstances, speak to a qualified accountant or contact HMRC directly.
Nothing here creates a professional relationship, and no liability is accepted for decisions taken on the basis of a calculation. That is the honest position, and it is why the working is shown: so you can check it rather than rely on it blindly.
How it is funded #
The calculators and guides are free, with no signup and no email wall. The site is funded by advertising, served by third-party networks, and that side is kept entirely separate from the editorial one.
Advertisers have no say in what is written, which products appear in a comparison, or how they are ranked. Comparison pages are built from published list prices, and where a price could not be read from the vendor's own pricing page, the page says so on its face rather than presenting an unconfirmed figure as verified.
What the site does with data, including advertising and analytics cookies, is set out in the privacy policy.
Contact #
Corrections, questions, and suggestions for tools that do not exist yet: get in touch.