Self-employed tax calculator
Turnover in, expenses off, and what the tax bill actually looks like on the profit that is left.
How this is calculated
Tax is charged on profit, not turnover. Profit is your business income less allowable expenses, and it is that figure everything below is calculated on.
Income tax applies band by band exactly as it does for an employee, with the same £12,570 personal allowance.
Class 4 National Insurance replaces the employee Class 1 charge. It is 6% on profit between £12,570 and £50,270, then 2% above, and it is collected through Self Assessment alongside the income tax.
Class 2 is no longer a separate charge for most people. Profits above the small profits threshold are treated as having Class 2 paid, so State Pension entitlement builds without an extra payment.
Rates used · 2026/27
| Personal allowance | £12,570 |
| Income tax | 20%, 40%, 45% as usual |
| Class 4 NI | 6% from £12,570 to £50,270 |
| Class 4 NI above £50,270 | 2% |
| Payments on account | due if the bill exceeds £1,000 |
| Self Assessment deadline | 31 January online |
Last checked July 2026. Source: HMRC and gov.uk.
Worked example
On £55,000 of turnover with £9,000 of expenses the taxable profit is £46,000. Income tax is £6,686 and Class 4 National Insurance is £2,006, so £8,692 in total, leaving £37,308. Because the bill exceeds £1,000 you also make payments on account of £4,346 each.
Common questions
What are payments on account?
If your bill exceeds £1,000 HMRC asks for half of it again in January and another half in July as an advance on next year. In your first year that means paying roughly one and a half times the bill at once, which catches people out badly.
Is this the same as a limited company?
No. A company pays corporation tax on profit and you are taxed separately on the salary and dividends you take. Use the dividend tax calculator for that.
Does it cover Scotland?
Not yet. Scotland sets its own income tax bands, so the income tax part would differ. Class 4 National Insurance is the same across the UK.
What counts as an allowable expense?
Costs incurred wholly and exclusively for the business. Mixed-use costs like a phone or a car have to be apportioned to the business share.