Self-employed tax calculator.
Estimate the Income Tax and National Insurance due on your self-employed profit for the year. This is an estimate for general guidance only, not personalised tax advice — talk to Buzz for advice specific to your situation.
Enter your estimated profit
Enter your estimated profit, then click Calculate to see an estimate.
Rates used in this calculator (2026/27 tax year)
| Income Tax band | Rate |
|---|---|
| Up to £12,570 (personal allowance) | 0% |
| £12,571 – £50,270 | 20% |
| £50,271 – £125,140 | 40% |
| Over £125,140 | 45% |
| Class 4 National Insurance (self-employed) | Rate |
|---|---|
| Up to £12,570 | 0% |
| £12,571 – £50,270 | 6% |
| Over £50,270 | 2% |
Class 2 National Insurance is no longer compulsory: if your profit is £7,105 or more it's treated as paid automatically (protecting your State Pension record at no cost), and below that it's only payable if you choose to pay voluntarily (£3.65/week). Not included in the total above. Source: gov.uk Income Tax rates and Self-employed National Insurance rates pages, checked July 2026.
What the calculator is doing to your number
Step one — it starts from profit. Turnover minus allowable business expenses. If you enter your sales figure instead, the answer will be far too high.
Step two — Income Tax, in bands. The first £12,570 is covered by the personal allowance. The next slice up to £50,270 is taxed at 20%, then 40% to £125,140, then 45%. Only the portion inside each band is taxed at that band's rate, so landing in the 40% band does not make all your profit 40%.
Step three — Class 4 National Insurance. 6% on profit between £12,570 and £50,270, then 2% above that. It runs alongside Income Tax on the same profit.
Step four — Class 2. No longer a compulsory charge. If your profit is £7,105 or more it is treated as paid, protecting your State Pension record at no cost. Below that you can pay voluntarily at £3.65 a week if you want the qualifying year.
One more thing the calculator cannot know: if your profit rises above £100,000 the personal allowance tapers away, which is handled automatically, but pension contributions, Gift Aid and other income all shift the result.
£45,000 of profit, start to finish
- Taxable profit£45,000
- Income Tax — (£45,000 − £12,570) × 20%£6,486
- Class 4 NI — (£45,000 − £12,570) × 6%£1,946
- Total due for the year£8,432
- Left after tax£36,568
Now the bit that catches people out. That £8,432 is 18.7% of profit — but it is not what leaves your account in your first January. Once your bill is over £1,000, HMRC also collects payments on account towards the following year: half the bill on 31 January and half on 31 July.
- Due 31 January — the year's tax plus the first payment on account£12,648
- Due 31 July — second payment on account£4,216
So the first January costs 28% of that year's profit, not 18.7%. It settles down afterwards, because from then on you are always half paid up in advance — but the first one is the reason so many first-year sole traders get a shock. Set money aside from month one.
Three sensible next steps
- Open a separate tax account and move money into it weekly. A percentage of every payment received, not whatever is left at the end of the month. On these figures, 25% covers the bill and the first payment on account with a little room.
- Check your expenses are complete before you judge the number. Use of home, mileage, phone, professional subscriptions, training and equipment are the ones most commonly missed. Every £1,000 of genuine expense you have forgotten is £260 of tax and NI at these rates.
- Look at whether a limited company suits you. Not automatically — the gap between the two has narrowed and it brings extra filing. See when to switch, then check the numbers with us.
Common questions about self-employed tax
Is this worked out on turnover or profit?
Profit — turnover minus allowable business expenses. Entering turnover will produce a figure far larger than you actually owe, which is the single most common misreading of any self-employed tax tool. Profit here means the taxable figure after allowable costs but before any personal allowances, pension contributions or other reliefs. If you are not sure what your allowable expenses come to, that is the number to establish first, because everything else follows from it and estimating it loosely is how people end up with an unpleasant surprise in January.
When do I have to pay it?
By 31 January after the end of the tax year, together with your first payment on account for the following year if your bill is over £1,000. The second payment on account follows on 31 July. So a first full year can bring the whole liability plus half of it again on the same January date. Late payment attracts interest from the due date, plus penalties at 30 days, six months and twelve months. Filing late is penalised separately — an automatic £100 even if no tax is due. See key tax dates.
What are payments on account?
Advance instalments towards next year's tax, each normally half of the previous year's liability, due on 31 January and 31 July. They are not an extra tax; they are the same tax collected earlier, and once you are in the cycle the January payment covers a balancing amount plus a new instalment. If your income has genuinely fallen you can apply to reduce them — but reduce them too far and HMRC charges interest on the shortfall, so base the reduction on a real forecast rather than optimism.
Do I still pay Class 2 National Insurance?
Not as a compulsory charge. Where profit is £7,105 or more it is treated as paid, so your State Pension record is protected at no cost. Below that you can pay voluntarily at £3.65 a week to keep the year qualifying, which is usually worth doing — a qualifying year is cheap at that price compared with buying it back later at Class 3 rates. Class 4 is the one in the calculator: 6% between £12,570 and £50,270, then 2% above. Neither is deductible against your profit.
What is not included in this estimate?
Quite a lot, deliberately, to keep it usable. It assumes self-employment is your only income and takes no account of employment income, dividends, rental profit, savings interest, pension contributions, Gift Aid, the High Income Child Benefit Charge, student loan repayments or the personal allowance taper above £100,000. Any of those can move the number substantially — a second income source in particular, because it uses up the bands the calculator assumes are free. Use it to budget a reserve, not to decide what to draw.
Does Making Tax Digital change what I owe?
No. It changes how you report, not how much you pay, and the payment dates of 31 January and 31 July do not move. From your mandation date — April 2026 for qualifying income over £50,000, April 2027 over £30,000 and April 2028 over £20,000 — you keep digital records and send quarterly updates plus an End of Period Statement and Final Declaration. The practical effect is that the figure in this calculator stops being an annual surprise and becomes something you can see through the year. See the MTD guide.
