This page shows income tax and Class 4 NI with a quarterly set-aside estimate using current 2026/27 assumptions. Compulsory Class 2 NI ended from April 2024 (it is now voluntary if profits are under £7,105).
Updated for 2026/27 · Reviewed by James Whitfield · Methodology and assumptions
| Annual profit | £18,000.00 |
| Personal allowance | £12,570.00 |
| Taxable income | £5,430.00 |
| Income tax — Basic rate (20%) | £1,086.00 |
| Income tax — Higher rate (40%) | £0.00 |
| Income tax — Additional rate (45%) | £0.00 |
| Class 4 NI — £12,570 to £50,270 (6%) | £325.80 |
| Class 4 NI — Above £50,270 (2%) | £0.00 |
| Total deductions | £1,411.80 |
| Net income | £16,588.20 |
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Monthly net income
£1,382.35
Weekly net income
£319.00
Effective deduction rate
7.8%
Set aside £352.95 per quarter as a savings estimate (a quarter of the year's income tax and Class 4 NI). Self Assessment is paid on 31 January and 31 July, usually as two payments on account of half the previous year's bill. First year: there are no payments on account yet, so your first 31 January bill is the whole year-one bill plus the first payment on account for year two — up to 150% of a year's tax on one date. Save extra before your first January. How quarterly tax works.
For £18,000 profit, the estimate combines income tax by band, Class 2 NI (where applicable) and Class 4 NI, then shows total deductions and net income.
Self-employed people pay Class 4 NI: 6% on profits between £12,570 and £50,270 and 2% above. Class 2 NI stopped being compulsory from April 2024, so it is not included.
About £352.95 a quarter as a savings estimate: a quarter of the year's income tax and Class 4 NI. HMRC collects it on 31 January and 31 July, normally as two payments on account of about £705.90 each. In your first year there are no payments on account yet, so the first 31 January bill can be up to 150% of a year's tax.