Self-Employed Tax Calculator (Sole Trader)
If you are self-employed, you pay Income Tax and Class 4 National Insurance on your taxable profits, not your turnover. Profits are what is left after deducting your allowable business expenses.
Enter your annual turnover and expenses to see your taxable profit, the tax you will owe through Self Assessment, and what you keep.
How the calculation works
We believe numbers should be transparent. Here is the formula behind this calculator.
Worked example
Worked example: £40,000 turnover in 2026/27
Examples at common levels
See how the numbers change at typical input levels, using the updated for tax year 2026/27 rates.
| Scenario | Estimated tax & NI due | Profit after tax | Taxable profit | Income Tax | Class 4 National Insurance | Student loan repayment | Class 2 National Insurance |
|---|---|---|---|---|---|---|---|
| £20,000 turnover, £2,000 expenses Basic rate only | £1,411.80 | £16,588.20 | £18,000.00 | £1,086.00 | £325.80 | £0.00 | Treated as paid |
| £40,000 turnover, £5,000 expenses Matches the worked example | £5,831.80 | £29,168.20 | £35,000.00 | £4,486.00 | £1,345.80 | £0.00 | Treated as paid |
| £80,000 turnover, £10,000 expenses Higher-rate income tax | £18,088.60 | £51,911.40 | £70,000.00 | £15,432.00 | £2,656.60 | £0.00 | Treated as paid |
| £150,000 turnover, £15,000 expenses Additional rate band | £50,909.60 | £84,090.40 | £135,000.00 | £46,953.00 | £3,956.60 | £0.00 | Treated as paid |
Important assumptions
- Assumes all income is self-employed profit and all expenses are allowable.
- Class 2 is treated as paid when profits exceed the Small Profits Threshold, so no Class 2 is payable.
- Class 4 NI is 6% on profits between £12,570 and £50,270 and 2% above £50,270.
- Student loan repayments are based on total income, so this is an estimate.
- Income tax uses England, Wales and Northern Ireland rates. Scottish rates differ.
Rates & official sources
Every calculation is based on the official rates and rules published by GOV.UK and HMRC.
Frequently asked questions
Do I pay Class 2 National Insurance?
Not since 2024/25 if your profits are above the Small Profits Threshold — your Class 2 contributions are treated as paid, which keeps your National Insurance record up to date. Below the threshold you can pay voluntarily.
What is the difference between turnover and profit?
Turnover is everything you receive for your goods or services. Profit is what is left after deducting your allowable business expenses — and it is your profit, not your turnover, that you pay Income Tax and Class 4 NI on.
When do I pay my self-assessment tax?
Your 2026/27 tax bill is usually due by 31 January 2028. Payments on account of roughly half of the bill are also due in January and July, so plan your cash flow early.
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View calculatorRelated guides
New to the topic? Read a plain-English guide on business & self-employed, with worked examples and tips.
Self-employed tax explained
Income tax and Class 4 NI on your profits, simply explained.
Read the guide BusinessSole trader vs limited company
The pros, cons and tax differences of each trading structure.
Read the guide BusinessHow to become self-employed
Registering with HMRC, tax returns and what you need to do first.
Read the guide BusinessMileage allowances explained
The HMRC mileage rates — 55p per mile for cars and vans in 2026/27, plus motorcycles, bicycles and passenger claims.
Read the guideThese calculations are estimates for guidance only and are not professional financial, tax or legal advice. UK rates and rules change, so always verify important figures with official GOV.UK / HMRC information or speak to a qualified professional. See our full disclaimer.