How is self-employed tax calculated in the UK?

You pay Income Tax on your trading profit (turnover minus allowable expenses) after the Personal Allowance, plus Class 4 National Insurance on profits above £12,570 and a flat Class 2 NI if profits exceed £6,845. Payments are made via Self Assessment in two instalments.

What NI do the self-employed pay?

Class 4 NI is 6% on profits between £12,570 and £50,270 and 2% above that for 2024/25 rates (confirm 2026/27 rates on GOV.UK). Class 2 is a flat weekly amount if profits top £6,845.

When do I pay self-employed tax?

Through Self Assessment: a payment on account by 31 January and a second by 31 July, with the balancing payment the following January. Use our calculator to estimate the annual bill, then budget monthly.

2026/27 Tax Year

Self-Employed Tax Calculator (UK)

Estimate your income tax and National Insurance on self-employed trading profit for 2026/27, and see what you keep after tax. Enter your profit in our calculator — it handles the Personal Allowance, Income Tax bands and Class 4 NI.

How Self-Employed Tax Works

Three things determine your bill: the Personal Allowance, Income Tax bands, and National Insurance.

Component	2026/27 (England)
Personal Allowance	£12,570 (withdrawn above £100k)
Income Tax	20% to £50,270 · 40% to £125,140 · 45% above
Class 4 NI	~6% (£12,570–£50,270) · ~2% above (confirm on GOV.UK)
Class 2 NI	Flat weekly if profits > £6,845

💡 Worked example

🔧A sole trader with £40,000 profit pays Income Tax on £27,430 (£5,486) plus Class 4 NI on the profit band. Allowable expenses reduce your profit and therefore your bill — keep good records.

Self-Employed Tax Tips

Allowable expenses: office, travel, software, accountancy fees all reduce profit.
Payments on account: budget ~50% of your tax bill twice a year to avoid a January shock.
Pension: personal pension contributions extend your basic-rate band, cutting higher-rate tax.
Marriage Allowance: if your partner is a non-taxpayer you can transfer allowance.