Free tool

Self-Assessment Tax Calculator 2025/26

Estimate the Income Tax and Class 4 National Insurance you'll owe as a UK sole trader. Enter your self-employed income and allowable expenses to see how much to set aside.

Estimated tax & NI to set aside

£0.00

Taxable profit£0.00
Income Tax£0.00
Class 4 National Insurance£0.00
Total tax + NI£0.00
Take-home after tax£0.00

Assumes self-employed (sole trader), no other income, standard Personal Allowance. Class 2 NI is no longer payable for most. Student loan repayments not included.

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Frequently asked questions

How is sole-trader tax calculated?

Your taxable profit is your income minus allowable business expenses. You pay Income Tax on profit above your Personal Allowance (£12,570) at 20%, 40% and 45% bands, plus Class 4 National Insurance at 6% on profit between £12,570 and £50,270 and 2% above that.

How much should I set aside for tax?

A common rule of thumb is 20–30% of your profit, but it depends on your income. This calculator gives a more precise figure by applying the actual 2025/26 tax and National Insurance bands to your numbers.

Do I still pay Class 2 National Insurance?

For most self-employed people, mandatory Class 2 NI was removed from 2024/25 onwards — you still get the National Insurance credit toward your State Pension without paying it. It remains voluntary if your profits are below the small-profits threshold.

When is the self-assessment deadline?

For online returns, the deadline is 31 January following the end of the tax year (which runs 6 April to 5 April). Any tax owed is also due by 31 January, with payments on account potentially due in January and July.

What counts as an allowable expense?

Costs incurred wholly and exclusively for your business — such as stock, equipment, business travel and mileage, a proportion of home-working costs, software, and professional fees. Keeping accurate records (as FTrak does) makes this straightforward.

Never scramble at self-assessment again

FTrak logs your income, mileage, hours and receipts through the year, so your figures are ready when the deadline comes.

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Estimates are for guidance only and are not tax advice. Figures use 2025/26 rates for England, Wales & Northern Ireland. Confirm with HMRC or an accountant.