Comparison · Tax · 2026/27
Second Job Tax Code vs Self-Employed Side Income UK 2026/27
Extra income can come as a second PAYE job, usually taxed under a BR tax code at a flat 20%, or as self-employed side income, taxed via Self Assessment with expenses deducted. This 2026/27 guide compares how each is taxed and National Insurance treated, and which suits different kinds of extra work.
TL;DR — 30-Second Summary
- • Second job (BR code): taxed at 20% flat from the first pound, no Personal Allowance
- • Self-employed side income: £1,000 trading allowance, then tax on profit after expenses
- • Personal Allowance: £12,570 for 2026/27 — can sometimes be split between two PAYE jobs
- • NI: Class 1 (8%/2%) on each PAYE job separately; Class 4 (6%/2%) stacks on self-employed profit
- • Register with HMRC if self-employed gross income exceeds £1,000 in the tax year
How Each Is Taxed
| Feature | Second PAYE job | Self-employed side income |
|---|---|---|
| Tax-free allowance | None (BR code) unless split by HMRC | £1,000 trading allowance |
| Expenses deductible? | Limited employment expenses only | Yes — genuine business costs |
| Tax collected | Deducted automatically at source | Self Assessment, paid Jan/July |
| National Insurance | Class 1: 8% (£12,570-£50,270), 2% above | Class 4: 6% (£12,570-£50,270), 2% above |
Which Should You Choose?
The choice usually comes down to the nature of the work rather than tax alone — a genuine second employer relationship is a PAYE job; freelance, consultancy or trading activity is self-employment, and HMRC expects you to classify it correctly rather than pick whichever is cheaper. If you do have a genuine choice, self-employed side income can be more tax-efficient for modest amounts thanks to the trading allowance and expense deductions, but budget carefully for the January tax bill. Check your combined take-home with the take-home pay calculator and compare PAYE vs self-employed for the wider picture.