Self-Employed Tax Calculator
Work out your Income Tax, Class 2 and Class 4 National Insurance as a sole trader — plus whether you’ll need to make payments on account.
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How to use this calculator
This estimates your Self Assessment bill for trading profits alone — it doesn’t include other income, pension contributions, or student loan repayments.
Enter your turnover
Your total trading income for the tax year, before any expenses are deducted.
Choose how you deduct costs
Enter your actual allowable expenses, or use the £1,000 trading allowance instead if that’s simpler or larger.
See your bill and your deadlines
Get your Income Tax, both classes of National Insurance, your take-home profit, and whether payments on account apply.
How it’s worked out
Income Tax on self-employed profits
Your trading profit — turnover minus allowable expenses (or the £1,000 trading allowance) — is taxed through the same Income Tax bands as employment income: 20% basic rate, 40% higher rate, and 45% additional rate, after your Personal Allowance of £12,570. If your profit is over £100,000, your Personal Allowance is reduced by £1 for every £2 over that threshold, reaching £0 at £125,140 — this calculator applies that taper automatically.
National Insurance
Class 2 and Class 4 — what’s actually changed
Class 4 National Insurance is charged at 6% on profits between £12,570 and £50,270, and 2% above that — collected through Self Assessment alongside your Income Tax.
Class 2 is different from what many older guides describe. Since 2024/25, if your profits are £7,105 or more, you get a National Insurance qualifying year automatically credited for free — you don’t pay Class 2 at all. Below £7,105, Class 2 becomes voluntary: you can choose to pay £3.65 a week (£189.80 a year) to protect your State Pension record for that year, but you don’t have to.
Deducting costs
Actual expenses or the trading allowance?
You can deduct your actual allowable business expenses — costs that are wholly and exclusively for your trade, like office costs, travel, stock, insurance and use of home as office. Or, if it’s simpler, you can deduct the £1,000 trading allowance instead. You can’t use both in the same tax year — it’s whichever gives you the better result, not a top-up on top of your real expenses.
If you use a vehicle for business travel and claim simplified mileage expenses instead of actual running costs, HMRC’s rate for cars and vans rose from 45p to 55p per mile (first 10,000 business miles a year) from 6 April 2026 — the first increase since 2011. The rate for the miles above 10,000 stays at 25p, and motorcycles stay at 24p.
Cash flow
Payments on account
If your Self Assessment bill (Income Tax plus Class 4 NI) is over £1,000, and less than 80% of your tax was collected at source, HMRC normally asks you to make two advance “payments on account” toward next year’s bill — each one half of this year’s total, due 31 January and 31 July. You then pay or reclaim the difference as a balancing payment the following 31 January, once your actual profit for that year is known.
Deadlines
Key Self Assessment dates
Register for Self Assessment by 5 October after the end of the tax year you started trading in. File a paper return by 31 October, or file online and pay any tax owed by 31 January — all measured from the end of the tax year (5 April) you’re reporting on.
Questions
Common questions
Do I have to pay Class 2 National Insurance?
Only if you want to. If your profits are £7,105 or more, you get the qualifying year for free without paying anything. Below that, paying £3.65 a week is optional — mainly worth it if you want to protect a State Pension qualifying year for a low-profit or part-time year.
What if my expenses are more than my turnover?
That’s a trading loss, which this calculator doesn’t model — it floors taxable profit at £0. Losses can often be carried forward or offset against other income, but that depends on your wider tax position, so it’s worth getting advice from an accountant or HMRC directly.
Does this include my other income?
No — this only estimates tax on the trading profit you enter. If you also have employment income, rental income, or other self-employment, your actual Personal Allowance use and tax band could differ, since all your income is added together for Income Tax purposes.
Why does my region affect the result?
Income Tax bands are different in Scotland, which sets its own rates. National Insurance (Class 2 and Class 4) is set UK-wide and doesn’t change by region, which is why only the Income Tax portion changes here.
Should I use actual expenses or the trading allowance?
Whichever is larger. If your genuine allowable expenses are under £1,000, the trading allowance usually gives you a bigger deduction with less record-keeping. If your real expenses are higher, claiming them properly will usually reduce your tax bill more.
Where these figures come from. Income Tax rates, bands and the Personal Allowance taper are taken from gov.uk. Class 2 and Class 4 National Insurance rates and thresholds, the trading allowance, payments on account rules, Self Assessment deadlines and the simplified mileage rate are all taken from gov.uk. Figures checked on 24 September 2026.
Self-employed National Insurance rates (gov.uk) · Trading allowance (gov.uk) · Payments on account (gov.uk) · UK Income Tax Calculator
How we calculate · Editorial policy. This is general information, not tax advice.