Own product
PayReckon.
UK take-home pay calculators for contractors and employees — inside IR35 through an umbrella, outside IR35 through your own limited company, or permanent on PAYE, all behind one tax engine so the comparison is genuinely like for like.
Covers
- 2024/25, 2025/26 and 2026/27 tax years
- Rest-of-UK and Scottish income tax
- Tax codes and NI category letters
- Student loan plans 1, 2, 4, 5 and postgraduate
- Three pension relief methods
- Blind Person's and Marriage Allowance
The problem
Three arrangements, three different answers.
Deciding how to be paid in the UK is genuinely hard to reason about. A day rate and a salary are not comparable numbers, and most calculators handle one arrangement in isolation — so comparing them means running three different tools that disagree with each other and hoping the difference is real rather than a modelling artefact.
What it does
One tax engine behind all three.
PayReckon runs all three arrangements through the same tax engine. Income tax, National Insurance, dividend tax, and student loan repayments are calculated by shared code, so identical taxable income is taxed identically no matter which arrangement produced it. The calculators diverge only where the tax treatment genuinely does.
The calculators
Every route you can be paid through.
Umbrella company
Assignment rate through to take-home: umbrella margin, employer's NI, Apprenticeship Levy, employer pension, and rolled-up versus accrued holiday pay.
Limited company
Corporation tax with marginal relief, salary and dividend strategy, expenses, Employment Allowance, joint ownership, and Business Asset Disposal Relief.
PAYE salary
Bonus, overtime, cash allowances, benefits in kind, and pension contributions across all three relief methods.
Why the numbers hold
A calculator is only worth the rigour behind it.
Solved, not approximated
In an umbrella calculation, employer's NI, the Apprenticeship Levy, and employer pension are deducted from the assignment rate but charged on the gross pay that remains — each depends on the other. PayReckon solves that relationship algebraically per NI branch, and a round-trip test asserts that gross pay plus every employment cost returns the assignment rate exactly.
Every rate cited to source
Figures come from gov.uk and gov.scot with the source URL recorded beside the number. Rates are never edited in place when a new tax year arrives — a new file is added, so historical calculations stay reproducible.
Correctness held by tests
The calculation layer is pure, unit-tested functions with no UI code involved in any calculation, so the engine can be verified independently of how it is displayed.
Accessibility enforced, not eyeballed
A palette check holds every text colour to WCAG AA against the surface it actually renders on, and verifies no two chart fills collapse into each other under protanopia, deuteranopia, or tritanopia. It exits non-zero, so a change that breaks contrast cannot land quietly.
Who uses it
Built for people making the decision.
Independent contractors
Weighing a contract against a permanent offer, or working out what a day rate is genuinely worth once employment costs and tax are accounted for.
Consultancies and small businesses
Modelling what an engagement actually costs, and understanding the difference between engaging someone inside or outside IR35.
Anyone going independent
Leaving employment for the first time and trying to work out whether the numbers hold up before committing.
Why it is on this site
PayReckon is not a security product, and it is not client work. It is here because it is the same discipline applied to my own codebase: correctness held by tests rather than by care, every figure traceable to its source, and automated gates that fail the build rather than relying on someone remembering to check.
That is what I am asking clients to trust me with. This is where it is visible.
Work out what you would actually take home.
Put your numbers in and compare all three arrangements side by side.
PayReckon produces estimates for planning purposes and is not financial advice. Confirm your position with a qualified accountant before acting on it.
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