FullWorkings UK tax and finance calculators

Self-employed tax

2026-27

Your trade

TurnoverEverything the business invoiced or took this tax year, before expenses. £
Allowable expensesWhat you can deduct. Leave blank if you are entering profit above. £
Other incomeA salary, pension or rent taxed alongside this. It raises the Income Tax on your profits but not the National Insurance. £
Where you liveScotland sets its own Income Tax rates, but not National Insurance.

What the profits cost

Tax and National Insurance £0.00 a year
Turnover£0.00
Profit£0.00
Income Tax on the profit£0.00
Class 4 National Insurance£0.00
Class 2 National Insurance—
Left after tax£0.00

Rates

Effective rate on the profit—
Rate on the next £100—
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How this is worked out

A sole trader pays Income Tax on their profit and Class 4 National Insurance on top of it. Those are two separate charges with two separate thresholds, and they are the whole bill.

Class 2 is no longer a charge

⚠ This changed in April 2024 and a lot of calculators have not caught up. If your profit is at or above the small profits threshold, Class 2 is treated as paid — your National Insurance record is credited and nothing is taken. Adding a weekly Class 2 charge to a profitable trader's bill over-states it by roughly £190 a year.

Below that threshold nothing is due either, but nothing is credited — so the year does not count toward your State Pension unless you choose to pay voluntarily. That is the situation where Class 2 is worth thinking about, and it is the opposite of the one people usually ask about.

National Insurance is charged on the profit alone

Other income raises the Income Tax on your profits, because Income Tax is charged on everything added together. It does not raise the Class 4, because National Insurance is charged per source. Someone with a £50,000 salary and £10,000 of profit still pays the main Class 4 rate on that profit, not the 2% rate that their total income might suggest.

Why the Income Tax figure is a difference

Your profits sit on top of any other income, so the tax they cost is what your bill rises by — not the tax on the profits taken on their own. Working them out in isolation would give you the Personal Allowance twice and report almost nothing.

Class 4 is worked out on the year

An employee's National Insurance is recalculated on every payslip, which is why a bonus month can be taxed oddly. Class 4 has no pay periods: profit is an annual figure, and it is a single calculation on the year.

What this does not cover

Student loan repayments, which Self Assessment does collect but which are worked out differently for the self-employed than through payroll. Payments on account, which are a timing question rather than an amount. The £1,000 trading allowance. Capital allowances on equipment. Losses carried in from another year. Partnerships, which split profit before any of this applies. And Class 1 National Insurance on any employment income, which your employer has already deducted.

Where these figures come from

Every rate above is read from a dated rate file rather than written into the page, and each one is checked against the gov.uk page it came from. How these numbers are kept right sets out the whole process.

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