Self-employed tax calculator UK 2026/27
That is £594.32 a month. Income tax £5,486.00 plus Class 4 National Insurance £1,645.80. You keep £32,868.20, which is 82.2% of your profit.
Class 2 National Insurance: nothing to pay, your profit is over £7,105 so it counts as paid.
Your bill, line by line
| Line | Rate | Profit in band | Tax |
|---|---|---|---|
| Personal allowance | 0% | £12,570.00 | £0.00 |
| Basic rate | 20% | £27,430.00 | £5,486.00 |
| Higher rate | 40% | £0.00 | £0.00 |
| Additional rate | 45% | £0.00 | £0.00 |
| Class 4 NI, main rate | 6% | £27,430.00 | £1,645.80 |
| Class 4 NI, above £50,270 | 2% | £0.00 | £0.00 |
| Class 2 NI | £3.65 a week | treated as paid | £0.00 |
| Total | £7,131.80 |
Quick answers
How much tax do I pay on £40,000 profit?
£7,131.80 in 2026/27: £5,486 income tax and £1,645.80 Class 4 National Insurance. That leaves £32,868.20, about £2,739 a month.
What are Class 2 and Class 4 National Insurance?
Class 4 is 6% of profit between £12,570 and £50,270 and 2% above that, paid with your Self Assessment. Class 2 is £3.65 a week; with profit of £7,105 or more it counts as paid without you paying anything, and below that you can pay it voluntarily to protect your State Pension record.
How is this different from being employed?
An employee on £40,000 pays £2,194.40 National Insurance at 8%; self-employed Class 4 on the same profit is £1,645.80 at 6%. Income tax is the same. You get no employer pension or sick pay, and you pay the tax yourself in January.
Sources: GOV.UK income tax rates and Scottish income tax (checked 31 Oct 2026); GOV.UK self-employed National Insurance rates (checked 1 Nov 2026).