What HMRC actually takes from £12,000 of side income depends on the salary it sits on top of. £1,000 is covered by the trading allowance; the remaining £11,000 is taxed at your marginal rate.
| Salary | Tax + NI | You keep | Effective rate |
|---|---|---|---|
| £15,000 | £2,200 | £9,800 | 18% |
| £20,000 | £2,200 | £9,800 | 18% |
| £25,000 | £2,200 | £9,800 | 18% |
| £30,000 | £2,200 | £9,800 | 18% |
| £35,000 | £2,200 | £9,800 | 18% |
| £40,000 | £2,346 | £9,654 | 20% |
| £45,000 | £3,346 | £8,654 | 28% |
| £50,000 | £4,346 | £7,654 | 36% |
| £60,000 | £4,400 | £7,600 | 37% |
| £80,000 | £4,400 | £7,600 | 37% |
| £100,000 | £6,600 | £5,400 | 55% |
Rules checked 18 August 2026 against GOV.UK pages showing the 2026/27 tax year. This is information, not tax advice; your Self Assessment is the authority on what you actually owe.