By profit
A £100,000 self-employed profit: tax and the allowance taper
Six figures exactly: the full tax-free allowance survives, but only just.
£100,000 of profit is the last figure at which a sole trader keeps the whole Personal Allowance of £12,570. In England, Wales or Northern Ireland the 2026/27 bill is £30,689, made of £27,432 Income Tax and £3,257 Class 4, which leaves £69,311; in Scotland it is £33,989. Beyond this point the allowance is withdrawn, £1 for every £2 of adjusted net income above £100,000, so every extra pound of profit is taxed itself and also makes another fifty pence taxable. Over the next £25,140 of profit, the cost of each pound reaches 62 % with Class 4 in the rest of the UK and 69.5 % in Scotland, until the allowance is gone at £125,140. Gross pension contributions are deducted when adjusted net income is measured, which is why a sole trader whose year ends above six figures can bring that income back to £100,000 and keep the full allowance.
Self Assessment bill 2026/27
£30,689
Put aside 30.7 % of your profit · next £100 of profit costs 62.0 %
| Profit | £100,000 |
| Income Tax | £27,432 |
| Class 4 National Insurance | £3,257 |
| Class 2 | treated as paid |
| Kept from your profit | £69,311 |
When you pay, if 2026/27 is your first year
| 31 January 2028: bill + first payment on account | £46,033 |
| 31 July 2028: second payment on account | £15,344 |
Each payment on account is half of £30,689 (Income Tax and Class 4, loans excluded). How payments on account work
Making Tax Digital at this turnover
Turnover of £100,000 is over the £50,000 test. If your 2024/25 return showed income like this, quarterly updates start on 6 April 2026. Check your start date
Figures checked by Radif Partners · Editorial policy · How we calculate
The final pound of a full allowance
The Personal Allowance is the one part of the Income Tax system that depends on the size of your income. Up to £100,000 of adjusted net income it stays at £12,570; past that, it is reduced, and at £125,140 nothing is left. A sole trader with exactly £100,000 of profit and no other income is on the last pound of the full allowance. A management consultant who adds £500 of bank interest is already over, which is why the figure on the return matters more than the profit in the accounts. The rule comes from section 35 of the Income Tax Act 2007 (legislation.gov.uk).
A 62 % slice above six figures
Above £100,000, a pound of profit is taxed at 40 %, and it also takes £0.50 off the allowance, which is then taxed at 40 % too. Add 2 % Class 4 and the combined cost is the figure in the last column below. Scotland applies its advanced rate of 45 % to the same mechanism, so the slice costs 69.5 % there, and a Scottish bill of £33,989 at six figures becomes £51,461 by the time the allowance has gone. The taper page covers the same effect for people with a salary as well as profit.
| Profit | Personal Allowance | Income Tax | Bill with Class 4 | Next pound costs |
|---|---|---|---|---|
| £100,000 | £12,570 | £27,432 | £30,689 | 62 % |
| £105,000 | £10,070 | £30,432 | £33,789 | 62 % |
| £110,000 | £7,570 | £33,432 | £36,889 | 62 % |
| £115,000 | £5,070 | £36,432 | £39,989 | 62 % |
| £120,000 | £2,570 | £39,432 | £43,089 | 62 % |
| £125,140 | £0 | £42,516 | £46,275 | 47 % |
Getting back to £100,000 with a pension
Adjusted net income is measured after gross pension contributions. Take a surveyor whose profit comes in at £110,000. Paying £8,000 into a personal pension, grossed up to £10,000 by the provider, brings adjusted net income back to £100,000, restores the whole allowance and cuts the Self Assessment bill by £4,000. The pension receives £10,000; the real cost is £4,000. Relief on this slice runs at the full taper rate rather than the ordinary higher rate, and Class 4 is left untouched. The pension relief calculator runs the same sum for other profits.
Six-figure paperwork
A business at this profit pays in instalments of £15,344, and if its turnover was similar in 2024/25, it has been inside Making Tax Digital since 6 April 2026, because the first wave covered qualifying income over £50,000 on that return. Quarterly updates do not change the amount of tax. They do make it easier to see, part way through the year, whether profit is heading past £100,000 while a contribution can still be made inside the tax year.