How we check our figures
A pay calculator is only useful if you can trust it. Here's exactly how we make sure the rates, thresholds and examples on The Kept Pound are right, and what we do when the rules change.
1. Official sources only
Every rate, threshold and allowance comes from the organisation that sets it:
- GOV.UK and HMRC: income tax, National Insurance, student loan thresholds, the tax-free allowances, dividends and savings, Child Benefit, pensions tax relief and the National Living Wage.
- The Scottish Government, through GOV.UK: Scottish income tax bands.
- NHS Employers: NHS Agenda for Change pay scales and High Cost Area Supplements.
- NHS Business Services Authority (NHS Pensions): NHS Pension contribution rates and what counts as pensionable pay.
We don't take figures from other calculator websites, forums or news articles. They're often out of date or disagree with each other. Where an official source doesn't confirm something, we leave it out rather than guess. For example, we don't state whether NHS unsocial hours payments are pensionable, because we couldn't find an official statement on it.
Each guide lists its sources at the bottom, and the salary, hourly and NHS pages link to the official tables they use.
2. One tested set of calculations
Every figure on the site, from the calculator to the salary tables and the examples in our guides, is produced by the same calculation code. Nothing is worked out by hand and typed in separately, so a page can't quietly disagree with the calculator.
That code is checked by more than 130 automated tests every time the site is updated. Among other things, they check:
- income tax, National Insurance and take-home pay against worked examples calculated by hand from HMRC rates, for England, Wales and Northern Ireland, and for Scotland
- every student loan plan, the three types of workplace pension, the £100,000 allowance taper, the Child Benefit charge, savings, dividends and tax codes
- all 93 NHS High Cost Area Supplement amounts against the official NHS Employers tables, to the pound
- every NHS Pension contribution tier boundary
If a single test fails, the update doesn't go live until it's fixed. The tests have already caught real errors. For example, they showed that NHS Employers rounds London supplements up to the next pound rather than to the nearest one, so we changed the calculator to match.
3. Checking the sources still work
Official websites move pages around. We regularly check every link to an outside source, and replace any that are broken or redirect elsewhere.
4. Reviews when the rules change
- Every April: new tax year rates, thresholds and allowances, and the new National Living Wage.
- After each UK Budget and Scottish Budget: any announced changes, such as frozen thresholds or new rates.
- After the NHS pay award: new Agenda for Change pay scales and pension tiers.
Each page shows when it was last updated.
What our figures can't tell you
We'd rather be upfront about the limits:
- Payslips are worked out each pay period. Our figures are yearly totals, so a month with a bonus or overtime will look different, even though the year should come out close.
- Some rare situations are simplified. For example, having two undergraduate student loan plans at once, the cap on K-code deductions, and Child Benefit counted as 52 weeks a year.
- Your own circumstances matter. Things like an emergency tax code, benefits taxed through your tax code, or tax owed from an earlier year change your real payslip.
- This is a guide, not advice. For decisions about your own money, check with HMRC or a qualified adviser.
Spotted something wrong?
Tell us. We check every report against the official source, and fix genuine mistakes as quickly as we can. Contact us, ideally with a Copy link from the calculator so we can see exactly what you entered.
Update log
- 2 November 2026: added this page.
- 1 November 2026: added the NHS pay calculator, a page for each NHS band and the NHS Pension guide, using NHS Employers and NHS Pensions 2026/27 figures. Checked every rate and claim on the site against official sources, corrected two inaccurate statements, fixed a broken source link and added official sources throughout. Added hourly-rate pages and guides on bonuses and London weighting.
- 31 October 2026: added guides on reading your payslip and emergency tax codes, and diagrams in the tax rate, 60% tax trap and pension guides.
- Late October 2026: launched The Kept Pound, covering the 2024/25, 2025/26 and 2026/27 tax years, and added salary-after-tax pages from £20,000 to £150,000.