UK self-employed tax calculator 2026/27

Estimate the Income Tax and Class 4 National Insurance on your sole-trader profit, and how much to put aside each month.

Estimated tax and NI on your profit

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Taxable profit
Method used
Income Tax on profit
Class 4 National Insurance
Put aside per month
Share of profit to put aside
Each payment on account (if due)

Keep the records that back this up. The UK Sole Trader Income & Expenses Tracker totals your income and expenses in the Self Assessment categories, adds flat-rate mileage (45p / 55p), and compares actual expenses with the £1,000 trading allowance.
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Rates used (England, Wales and Northern Ireland, 2026/27)

Personal Allowance £12,570, reduced by £1 for every £2 of income over £100,000.
Income Tax: 20% on the first £37,700 above your allowance, 40% up to £125,140, 45% above.
Class 4 NI: 6% on profits between £12,570 and £50,270, 2% above. Class 2 is no longer charged; with profits over £7,105 it's treated as paid. Below that you can pay voluntarily (£3.65 a week).
Trading allowance: £1,000 of tax-free trading income. You can use it instead of deducting actual expenses.

Worked example: £24,000 of income and £3,500 of expenses gives £20,500 profit. Income Tax is 20% × (£20,500 − £12,570) = £1,586. Class 4 NI is 6% × £7,930 = £475.80. Total £2,061.80, about £172 a month or 10% of profit.

When do I pay?

For 2026/27, the online Self Assessment return and any balance are due by 31 January 2028. If your bill is over £1,000 (and less than 80% was collected at source), HMRC also asks for two payments on account towards the next year, each half of this year's bill, due 31 January and 31 July. That's why a first-year bill can feel like 150% of what you expected. Making Tax Digital for Income Tax applies from 6 April 2026 if your qualifying income is over £50,000, and from April 2027 over £30,000.

I live in Scotland

Scottish Income Tax bands are different (starter 19% up to intermediate 21%, higher 42% and more), so this estimate will be off. Class 4 NI is the same across the UK.

What isn't included?

Student loan repayments, Class 2 voluntary contributions, savings and dividend income, Marriage Allowance, pension contributions, Gift Aid, capital allowances and losses from earlier years. Always check with GOV.UK or an accountant.

Sources: GOV.UK Income Tax rates, Self-employed NI rates, trading allowance. Estimate only; not tax advice.