UK tax calculators
Twelve calculators built on current HMRC rules — PAYE, self-assessment, dividends, CGT, side hustle, allowances and tapers — with AI explanations of what your numbers actually mean.
All tax calculators
From your monthly payslip to your January self-assessment bill — every UK tax decision in one place.
Salary take-home
PAYE, NI, student loan and pension on your gross pay
Self-employed tax
Income tax plus Class 2 and Class 4 NI on your profit
Side hustle tax
Etsy, eBay or freelance income on top of your day job
Dividend tax
Tax on dividends after the £500 allowance
Capital gains tax
CGT on shares, property and crypto disposals
Rental income tax
Income tax on BTL with Section 24 applied properly
Marriage allowance
Transfer £1,260 to a basic-rate partner, save £252
Salary sacrifice
Pension, cycle-to-work or EV scheme savings
Tax code checker
Decode 1257L, BR, D0, K and emergency M1/W1 codes
High income child benefit charge
Lose Child Benefit at £60-80k income
Crypto tax
CGT on crypto with bed-and-breakfast 30-day rule
Pension AA taper
Reduced annual allowance above £260k income
About tax calculators on Calclens
Calclens builds UK tax calculators that go one step further than the rest of the web — every result comes with a plain-English AI explanation, generated on demand. The calculation runs instantly in your browser. The AI layer is optional.
UK tax isn’t simple. Scotland has its own income tax bands, dividend tax has a separate allowance, self-employed people pay Class 2 plus Class 4 NI, salary sacrifice changes both income tax and NI, and high earners hit a tangle of tapers — Personal Allowance taper, pension Annual Allowance taper, and the High Income Child Benefit Charge. Generic global tax calculators flatten all of this. Ours don’t.
What makes these tax calculators different
- Current HMRC rules — PAYE thresholds, dividend allowance, CGT rates, Scottish income tax bands, NIC Classes 1, 2 and 4
- Honest interaction maths — side hustle on top of PAYE, salary sacrifice across tax and NI, marginal rate effects on dividend planning
- The traps no one explains — HICBC clawback, Personal Allowance taper at £100k, Annual Allowance taper above £260k, bed-and-breakfast rules on shares and crypto
- AI explanation layer — powered by Claude (Anthropic), explained in detail on the how AI works page
- Free forever — no sign-up, no accounts, no display ads, no affiliate links
- Built in public — formulas come from HMRC and FCA-referenced sources, documented on our methodology page
Which tax calculator should I use?
I’m employed and want to know my real take-home pay
Start with the salary take-home calculator — it applies current PAYE bands, NI, student loan deductions and pension contributions on your gross salary. If you’re in Scotland, it uses Scottish income tax bands automatically. If you’re sacrificing salary for pension or benefits, run the salary sacrifice calculator alongside it — you save on both tax and NI, which most quick calculators miss.
Do I need to do self-assessment?
If you’re fully employed under PAYE, usually no. You typically need self-assessment if you’re self-employed, earn over £1,000 from a side hustle, receive dividends above the allowance, sold shares or property at a gain, earn rental income, or your household income triggers the High Income Child Benefit Charge. The self-employed tax calculator shows what to set aside; side hustle tax covers the trading allowance and PAYE interaction.
Does my side income mean I owe tax?
The first £1,000 of trading income is covered by the trading allowance — below that you don’t even need to register with HMRC. Above it, you pay income tax and NI on the excess. The side hustle tax calculator shows exactly how much tax you’d pay at your PAYE marginal rate, since side income stacks on top of your day job.
I sold shares or crypto. When do I owe CGT?
If your total gains in a tax year exceed the CGT annual exempt amount, you pay Capital Gains Tax on the excess. The CGT calculator handles shares, property and crypto, with different rates for each. For crypto specifically, the crypto tax calculator applies the bed-and-breakfast 30-day rule, which catches a lot of people who sell and rebuy.
My income is around £60-80k. Why is my Child Benefit shrinking?
The High Income Child Benefit Charge claws back Child Benefit between £60k and £80k of the higher earner’s income. The HICBC calculator shows exactly how much you lose. It also shows whether contributing more to a pension would bring you under the threshold and keep the full benefit — often the cheapest way to keep it.
My tax code looks wrong
The tax code checker decodes the most common codes (1257L, BR, D0, D1, K codes) and flags emergency codes (M1, W1, X) that mean you might be overpaying. If your code looks wrong, you can challenge HMRC directly through your personal tax account — the calculator shows you what your tax-free allowance should look like for your situation.
Are these figures financial advice?
No. The calculators give you working numbers based on current HMRC rules. The AI explanation provides context, not regulated advice. For a binding decision — structuring dividends, claiming reliefs, or filing self-assessment — speak to a chartered accountant or qualified tax adviser.