Calculators › Self-Employed Tax Calculator (UK)
Self-Employed Tax Calculator (UK)
Enter your sales and expenses to see an instant estimate of your Income Tax and Class 4 National Insurance, and how much to set aside each month.
Tax year 2025/26 · Last reviewed 20 October 2026 · Prepared by the accountants at Self Assessment Tax Return Accountants (a trading style of Accotax). About us
A sole trader with £50,000 of profit in 2025/26 pays about £7,486 Income Tax plus £2,246 Class 4 National Insurance, around £9,732 in total. Enter your own turnover and expenses below to see your figure and how much to set aside each month.
How the calculator works
It takes your turnover, subtracts your allowable expenses (or the trading allowance if that is higher) to find your taxable profit, then applies Income Tax on top of any other income you have, plus Class 4 National Insurance on the profit. The result is the amount to set aside for your Self Assessment bill.
Rates used
| Personal allowance | £12,570 (reduced above £100,000) |
| Basic rate | 20% on the next £37,700 of taxable income |
| Higher rate | 40% up to £125,140 of taxable income |
| Additional rate | 45% above that |
| Class 4 National Insurance | 6% on profits between £12,570 and £50,270, then 2% |
| Trading allowance | £1,000 |
| Property allowance | £1,000 |
Rates for 2025/26, England, Wales and Northern Ireland. Check current HMRC guidance.
Payments on account
If your Self Assessment bill is over the payments-on-account threshold, HMRC normally asks for two advance payments towards next year, on 31 January and 31 July, each worth half of the previous bill. That is why many first-time filers are surprised by a much larger January bill.
What about Class 2 National Insurance?
Class 2 is no longer compulsory for the self-employed. You can still pay it voluntarily to protect your State Pension record if your profits are low.
Worked examples
These figures assume the profit is your only income and use the 2025/26 rates for England, Wales and Northern Ireland.
| Profit | Income Tax | Class 4 NI | Total | Per month |
|---|---|---|---|---|
| £20,000 | £1,486 | £446 | £1,932 | £161 |
| £30,000 | £3,486 | £1,046 | £4,532 | £378 |
| £50,000 | £7,486 | £2,246 | £9,732 | £811 |
| £80,000 | £19,432 | £2,857 | £22,289 | £1,857 |
| £110,000 | £33,432 | £3,457 | £36,889 | £3,074 |
Common mistakes
- Forgetting that payments on account double the first-year cash demand.
- Deducting private costs that HMRC will not allow.
- Ignoring Class 4 NI when budgeting.
Related services and guides
- Self Assessment for sole traders
- Self Assessment for Uber drivers
- Self Assessment for CIS contractors
- Self Assessment tax return cost
- Latest guides
Official sources
- Income Tax rates and Personal Allowances (GOV.UK)
- Self-employed National Insurance rates (GOV.UK)
- Payments on account (GOV.UK)
Frequently asked questions
Is this calculator accurate?
It is a good estimate using the published rates for the year shown. Your real bill depends on your full circumstances, such as pension payments, student loans, other income and Scottish rates.
Does it include student loan repayments?
No. If you have a student loan, repayments collected through Self Assessment are in addition to the figure shown.
What expenses can I deduct?
Costs incurred wholly and exclusively for your business, such as travel, equipment, software and professional fees. Personal costs cannot be deducted.
When is the tax due?
The balancing payment and first payment on account are due by 31 January after the tax year ends, and the second payment on account by 31 July.
Can an accountant lower my bill?
An accountant makes sure you claim every allowable expense and relief, which often pays for itself.
