Starting a new job should feel like a win. Then payday arrives and your net pay is hundreds of pounds lighter than expected. The culprit is often an emergency tax code — a temporary HMRC instruction that tells payroll to tax you more aggressively until your full history is loaded. It is usually fixable. It is rarely permanent. It is always annoying.
How UK tax codes work (30-second version)
Your tax code tells payroll how much tax-free pay to apply each year. Code 1257L means £12,570 of allowance spread across the year (the “1257” is allowance ÷ 10). Payroll uses a cumulative calculation so under-tax earlier in the year is caught up later. Emergency codes break that comfort — often taxing each pound without full allowance.
What BR actually does
BR means Basic Rate: payroll taxes all of that job’s pay at 20% — no personal allowance on that employment. Employee NI still runs as normal (8% in the main band for 2025/26). BR is common when HMRC has not yet linked your new job to your tax history — new starter without P45, second job, or delayed starter checklist processing.
BR is not “wrong” maliciously; it is a safe default so you do not underpay. Safe for HMRC. Less safe for your rent deposit.
£50,000 snapshot: 1257L vs BR
Normal 1257L
~£3,293/mo
~£39,520/year net
Emergency BR
~£3,084/mo
~£37,008/year net
That is about £209/month less take-home — roughly £2,500/year if BR never got fixed. On BR, you pay 20% on income that should have been tax-free via the £12,570 allowance — about £2,514 extra tax annually at £50k gross.
NI is identical in both scenarios (~£2,994 at £50k). Only Income Tax changes.
Other emergency codes
- 0T — no allowance; pay taxed through normal bands (20%, then 40%, then 45% as income rises). Harsher than BR at low salaries, fairer at very high salaries
- D0 — all pay taxed at 40% (higher-rate emergency). Brutal on a £50k salary
- D1 — all pay at 45% (additional rate). Rare. Dramatic
- W1 / M1 suffixes — “week 1 / month 1” non-cumulative: each payslip treated in isolation, not year-to-date. Can over-tax early in the year
On £50,000 with a D0-style 40% on everything, take-home can fall to roughly £2,250/month in simplified models — nearly £1,000/month below normal. If that is your payslip, call payroll today, not your group chat.
Why HMRC puts you on emergency tax
- No P45 from your previous employer when you started
- Starter checklist submitted as “Statement B or C” (no P45) — HMRC needs time to issue a proper code
- Second job — allowance may sit on your main job; second job gets BR until adjusted
- Company change — PAYE reference change can delay code transfer
- HMRC backlog — codes update asynchronously; payroll only applies what HMRC sends
Worked example: first month after job change
You earned £4,167 gross in month one (£50k salary). On 1257L cumulative, month-one tax might be ~£415. On BR, tax is 20% × £4,167 = £833 — roughly £418 extra tax in a single payslip. That is the “where did my money go?” moment.
When your code corrects to cumulative 1257L, later months may tax less to balance the year — or HMRC refunds via code adjustment next year.
Second jobs and BR
If your personal allowance is fully used on your main job, a second job is often coded BR by design — every pound taxed at 20% from pound one. That can be correct annually even if it feels harsh monthly. Check the HMRC app to see allowance allocation across employments.
What to do
- Give payroll your P45 or complete the starter checklist accurately on day one
- Check your tax code on the HMRC app or personal tax account within a week of starting
- Call payroll if code stays BR/D0 after a month with no explanation
- Model BR vs 1257L in TaxBite so you know the gap while you wait
- If you overpaid for the full year, HMRC usually refunds via adjusted code or Self Assessment — keep payslips
Official starter guidance: gov.uk/tax-codes.
Emergency tax vs bonus shock
A large bonus on a month 1 code can look like emergency tax even when your annual position is fine. Our bonus tax guide covers marginal rates; this guide covers structural code issues. Both can hit the same payslip — fun.
Model the gap in TaxBite
TaxBite supports tax code overrides under Advanced Features. Compare normal 1257L against BR on your salary to see monthly net and the Tax Bite difference.
See the BR bite →Bonus tax → · Pay rise take-home →
Estimates only — not tax advice. Emergency tax is often temporary. Payroll systems and cumulative calculations vary slightly from this simplified model.