How we check the figures

calcd is a money site, so the numbers have to be right. This page sets out where every statutory figure comes from, how we keep the calculators current, and what to do if you spot something wrong. It is the standard we hold ourselves to, in plain English.

Every figure traces to the body that sets it

A rate, threshold or allowance only goes into a calculator if it comes from the official source that decides it. For UK tax that means gov.uk and HMRC: income tax bands, National Insurance, dividends, capital gains, corporation tax, stamp duty (SDLT), VAT and pension allowances. Scottish income tax bands come from the Scottish Government, and the base rate from the Bank of England.

We record the exact source and the date we checked it against the figure in the code. Each calculator names the source it uses in its "About this calculator" note, with a link you can follow to the same gov.uk or HMRC page we read.

What we never treat as a source

We do not take a figure from another calculator, a tax or accountancy blog, a news article or an AI assistant. Those can point us towards a change, but the number itself always comes from the primary source. We use places like MoneyHelper and Citizens Advice only to sanity-check how we explain something, never to set a figure.

How we lock the logic

The rules live in code, not in a spreadsheet copied from somewhere else, and each tax calculator is pinned with worked examples we check by hand, so a known input always returns the known answer. A build check flags any calculator whose figures have fallen behind the current tax year before it can ship. Every result is broken down on the page so you can follow the working rather than take it on trust.

When we update

Tax rules move at set points in the year, and we go through the calculators each time: at the Budget, on 6 April for the personal tax year (income tax, National Insurance, dividends, pension allowances), on 1 April for the corporation-tax year, and whenever HMRC announces an in-year change. When a rate changes we update the figure, the page copy and the date together, then re-run the hand-checks.

Each calculator shows the tax year it is built for and the date its figures were last checked, so you can always see how current a number is before you rely on it.

Estimates, not advice

Every result is an estimate to help you plan. It is not financial, tax, legal or mortgage advice, and it cannot account for your full circumstances. For anything that matters, confirm the number with the relevant authority, your lender or a qualified adviser before you act on it.

Tell us if something looks wrong

Accuracy is the whole point, so we would rather know. If a figure looks off or a calculator does not behave as you expect, tell us through the contact form and we will look into it. You can read more about the project on the about page.