Self Assessment Tax Calculator 2026/27 (UK)

How It Works

If you are self-employed, nobody takes tax off your pay for you. You work out your own bill through Self Assessment, once a year, and it has three parts: Income Tax on your profit, Class 4 National Insurance on your profit, and Class 2 National Insurance — which, since April 2024, most self-employed people no longer pay at all. The starting point is your profit: turnover minus allowable business expenses. Tax is charged on profit, not sales, which is why keeping records of expenses matters.

Income Tax works the same way as for employees. The first £12,570 of profit is your Personal Allowance and is tax-free. Above that, in England, Wales and Northern Ireland, you pay 20% on the first £37,700 of taxable profit, 40% up to a total income of £125,140, and 45% above that. Above £100,000 the Personal Allowance shrinks by £1 for every £2, reaching zero at £125,140. Scotland sets its own bands for trading income — starter 19%, basic 20%, intermediate 21%, higher 42%, advanced 45% and top 48% — with the same allowance and taper.

Class 4 National Insurance is the self-employed equivalent of the NI an employee pays. In 2026/27 it is 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270. It is charged on your whole profit, not on profit after the Personal Allowance — but the lower limit happens to be the same £12,570 figure, so no Class 4 is due until your profit passes it. Class 4 does not count towards your State Pension; that is what Class 2 is for.

Class 2 National Insurance is the part that changed: compulsory Class 2 ended on 6 April 2024. If your profits are £7,105 or more (the Small Profits Threshold for 2026/27), Class 2 is treated as paid — the year counts towards your State Pension and you hand over nothing. Below £7,105 you pay nothing either, but the year only counts if you choose voluntary Class 2 at £3.65 a week (£189.80 a year). This calculator shows that option only when your profit is under the threshold.

The table below shows the total bill (Income Tax + Class 4, with Class 2 treated as paid) at different profit levels, for England, Wales and Northern Ireland:

Worked Example

A sole trader in England with £30,000 of profit in 2026/27. The Personal Allowance is the full £12,570, so taxable profit is £30,000 − £12,570 = £17,430. Income Tax is 20% × £17,430 = £3,486.00. Class 4 is 6% × £17,430 = £1,045.80. Class 2 is £0 — with profits over £7,105 it is treated as paid, so the year counts towards the State Pension at no cost. The total bill is £4,531.80, an effective rate of 15.1%, leaving take-home profit of £25,468.20. Setting aside £377.65 a month through the year covers the bill in full.

The same £30,000 profit for a Scottish taxpayer gives a slightly smaller bill. Taxable profit is again £17,430, but the Scottish bands split it: 19% × £3,967 = £753.73 (starter), 20% × £12,989 = £2,597.80 (basic) and 21% × £474 = £99.54 (intermediate) — £3,451.07 of Income Tax. Class 4 is the same UK-wide (£1,045.80), so the total is £4,496.87 — £34.93 a year less than in the rest of the UK, because the 19% starter rate undercuts the 20% basic rate. Above roughly £33,500 the Scottish bands cost more, as the 21% intermediate rate and the 42% higher rate (from £43,663) outweigh the starter-rate saving.

Assumptions

• One sole trade, 2026/27. The calculator taxes a single self-employment profit. Partnership shares, multiple trades and other income are not included.
• Standard Personal Allowance (£12,570), tapering above £100,000 and reaching zero at £125,140, in Scotland as well as the rest of the UK.
• Class 4: 6% on profits between £12,570 and £50,270, 2% above. Class 2: treated as paid (£0) at profits of £7,105 or more; voluntary £3.65 a week below that.
• Profit means turnover minus allowable expenses. If your total self-employed income is £1,000 or less, the trading allowance usually means you do not have to report it at all.
• Not included: pension contributions, student loan repayments, other income, capital allowances, VAT, and payments on account towards next year’s bill.

Sources: GOV.UK — Income Tax rates and bands; GOV.UK — Self-employed National Insurance rates; mygov.scot — Scottish income tax, current rates (6 April 2026 – 5 April 2027). Last reviewed: 13 November 2026.

How to Use This Calculator

Enter your annual profit — turnover minus allowable expenses — and choose your region. Results update as you type, so you can try different profit levels in seconds. The headline figure is your total Self Assessment bill for 2026/27, and the breakdown shows your Personal Allowance, taxable profit, Income Tax by band, Class 2 and Class 4, take-home profit, effective rate and monthly set-aside.

If your profit is under £7,105, a checkbox appears offering voluntary Class 2 at £3.65 a week. Tick it to add £189.80 a year to your bill; leave it unticked to see the bill with nothing paid for Class 2. Above £7,105 the checkbox disappears, because Class 2 is treated as paid automatically.

Tips and Practical Advice

Set the money aside monthly, from the start. The biggest shock for new sole traders is the first January bill: a £30,000 profit means £4,531.80 due on 31 January 2028 — and if your bill is £1,000 or more, HMRC usually also asks for payments on account, two advance payments each worth half this year’s bill, due 31 January and 31 July. That first January can demand 1.5 times your annual bill in one go. Putting the monthly set-aside figure into a separate account turns a cliff into a routine.

Know your deadlines. The online Self Assessment return for 2026/27 — and the balancing payment — is due by 31 January 2028; paper returns are due by 31 October 2027. A return filed even one day late triggers an automatic £100 penalty, with further penalties after three, six and twelve months, so file early even if you pay later: the penalty is for the late return, not the late payment.

Track your expenses properly: every allowable pound you record is a pound off your taxable profit, and at the basic rate £1,000 of missed expenses costs £260 in extra tax and Class 4 NI (20% + 6%). Check whether Making Tax Digital applies to you: it is being phased in for sole traders with qualifying income over £50,000 from April 2026, over £30,000 from April 2027 and over £20,000 from April 2028.

Finally, remember the trading allowance: if your total self-employed income for the year is £1,000 or less, you usually do not have to register or report it at all. It rises to £3,000 from 6 April 2027 (announced in Budget 2026) — useful if you are starting small, but once your income passes the allowance, keep proper records from day one.

Frequently Asked Questions