Estimate income tax and Class 4 National Insurance on your trading profits for 2026/27.
If you are self-employed, you pay income tax on your trading profit (revenue minus allowable expenses) through Self Assessment. The same income tax bands apply as for employees — 20% basic, 40% higher, 45% additional — but instead of PAYE, you file a tax return and pay your bill by 31 January following the end of the tax year.
Unlike employees, the self-employed also pay Class 4 National Insurance directly: 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270. Class 2 NI was abolished from April 2024, so there is no longer a flat weekly contribution. The Class 4 contributions still count towards your State Pension entitlement.
HMRC also requires payments on account — advance payments toward the next year's bill. Each payment is 50% of your prior year's Self Assessment tax liability, due on 31 January and 31 July. This means a newly self-employed person can face a large combined bill (prior year balance + first payment on account) in January.