Self-Employed Tax Calculator
Work out income tax and Class 4 National Insurance on your profit, how much to set aside, and how it compares with being employed.
Uses the standard personal allowance and Class 4 NI on profits. Class 2 is no longer payable. Trading allowance and other income are not modelled.
Your take-home profit a year
£3,047 a month · you keep 81.3% of your profit
That is about £703 a month into a separate tax pot, paid via Self Assessment.
An employee on £45,000 salary would take home £35,920 (employee NI is 8% against 6% Class 4). Employer NI and employment rights are not counted.
Where your profit goes
- Take-home£36,56881.3%
- Income tax£6,48614.4%
- Class 4 NI£1,9464.3%
What is taxed
You are taxed on profit (income minus allowable expenses), not turnover. Income tax uses the same bands and personal allowance as employees.
Class 4 National Insurance
Class 4 is 6% on profits between £12,570 and £50,270 and 2% above. Class 2 is no longer payable when profits exceed the small profits threshold, though your record is still protected.
Setting money aside
A useful rule is to save the percentage shown in the calculator from every payment you receive, so the Self Assessment bill (and payments on account) never surprises you.
Frequently asked questions
Figures use official GOV.UK 2026/27 rates. See the methodology.
How much tax do I pay on £40,000 profit? +
About £5,486 income tax plus £1,646 Class 4 NI at the 2026/27 standard allowance, so roughly 18% in total.
Does this include the trading allowance? +
No. If your gross trading income is £1,000 or less, you may not need to report it, and a £1,000 allowance can replace expenses. Treat this tool as a profit-based estimate.
What about payments on account? +
If your Self Assessment bill is over £1,000, HMRC usually asks for two advance payments toward the next year, each half of the bill.
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