Self-Employed Tax Calculator (UK)
If you're self-employed, you pay income tax on your profit plus Class 4 National Insurance, all through Self Assessment. This calculator estimates your combined 2026/27 bill.
How to use this calculator
- Enter annual profit (after expenses).
- Your results appear instantly below and update as you change the numbers.
How this calculator works
Your taxable profit is what's left after deducting legitimate business expenses from your income. Income tax uses the standard personal allowance (£12,570) and the 20/40/45% bands. On top of that, Class 4 National Insurance is charged at 6% on profits between £12,570 and £50,270 and 2% above — so the total marginal rate on profits in the main self-employed band is 26%. Class 2 NIC is treated as paid for profits over £12,570 and no longer produces a separate bill. You report the profit on a Self Assessment return and pay any tax due by 31 January. Worked example: £30,000 of profit costs £3,486 of income tax plus £1,046 of Class 4 NI — £4,532 total, an effective rate of 15.1%.
Frequently asked questions
What's the difference between Class 2 and Class 4 National Insurance?
Class 4 is a percentage of your profits (6% between £12,570 and £50,270, then 2%) — this calculator includes it. Class 2 was abolished as a payment for most people from 2024/25: if your profits are above the small profits threshold you are treated as having paid it, which protects your state pension entitlement at no cost.
When do I have to pay self-employed tax?
You register for Self Assessment by 5 October after the tax year ends, file your return online by 31 January, and pay what you owe by 31 January (plus a first payment on account of 50% of the next year's bill). If your tax plus Class 4 exceeds £1,000, HMRC collects payments on account twice a year.
Can I deduct expenses before the 6% Class 4 kicks in?
Yes. Class 4 is calculated on your taxable profit after all allowable expenses. Keeping receipts for working-from-home, travel, equipment and insurance genuinely lowers both your income tax and your Class 4 bill.
Disclaimer: Results are estimates for general information only and do not constitute financial, tax, or legal advice. Figures reflect the current tax year and may change. Always confirm current limits and consult a qualified professional before making decisions. Official figures: GOV.UK income tax rates · National Insurance · Stamp Duty Land Tax.