£40,000 Salary Plus £15,000 Side Profit: Tax Guide
Calculated combined take-home for a £40,000 main salary and £15,000 of self-employed profit, including Income Tax and the relevant National Insurance.
Direct answer: A £40,000 main salary plus £15,000 of self-employed profit produces about £43,228 annual take-home, or £3,602 a month. The calculation includes £9,432 of Income Tax and £2,340 of National Insurance.
Assumptions: England, Wales or Northern Ireland; 2026/27 rates; standard Personal Allowance; no pension, student loan or benefits; the figures are annualised. The side-income amount is profit after allowable business expenses, and Class 4 National Insurance applies to that profit.
The calculated combined position
| Item | Annual amount |
|---|---|
| Main salary | £40,000 |
| Self-employed profit | £15,000 |
| Total income before deductions | £55,000 |
| Income Tax across both incomes | £9,432 |
| Employee NI plus Class 4 NI | £2,340 |
| Combined take-home | £43,228 |
Why the incomes must be combined
Income Tax depends on total taxable income, not on each source viewed in isolation. The calculation therefore applies the tax bands to £55,000 in total. This avoids giving both sources a full Personal Allowance or treating the additional income as though it starts in the basic-rate band.
Employee National Insurance is calculated on the salary. Class 4 National Insurance is calculated separately on the sole-trader profit, while Income Tax uses the combined income.
Checks before using the monthly figure
- Check that HMRC has allocated the tax code between employments correctly.
- Keep business turnover separate from profit after allowable expenses.
- Add pension and student-loan deductions before setting a household budget.
- Use Scottish Income Tax bands if the taxpayer is resident in Scotland.
PAYE timing can move tax between payslips even when the annual total is unchanged. Self-employed income is normally settled through Self Assessment, so reserve the calculated liability rather than treating every receipt as spendable cash.
Official references and calculators
Figures use the 2026/27 Income Tax rates and National Insurance rates. Compare the individual amounts with the salary calculator, two-jobs calculator and self-employed calculator.