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 |
| Scotland, starter rate 19% | £12,571 to £16,537 |
| Scotland, basic rate 20% | £16,538 to £29,526 |
| Scotland, intermediate 21% | £29,527 to £43,662 |
| Scotland, higher rate 42% | £43,663 to £75,000 |
| Scotland, advanced rate 45% | £75,001 to £125,140 |
| Scotland, top rate 48% | Above £125,140 |
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 income tax and Class 4 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.
What is excluded from payments on account?
Student loan repayments and capital gains tax. They are due with the balancing payment in January but are not part of the twice-yearly advances. Payments on account are also not required at all if more than 80% of your tax was already deducted at source.
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?
Yes. Choose Scotland above and the six Scottish income tax bands are applied to your profit. Class 4 National Insurance is set UK-wide and does not change.
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.