Emergency tax codes: what 1257L W1/M1, BR and 0T cost you
Reading the common codes
| Code | What it does | Typical situation |
|---|---|---|
| 1257L | Normal code: £12,570 allowance, cumulative over the year | Standard employment |
| 1257L W1/M1 | Same allowance but each week/month taxed alone, no catch-up | New job, details still processing |
| BR | Flat 20% on everything, no allowance | Second job, or missing starter info |
| 0T | All bands apply but no allowance at all | No starter checklist and no P45 |
| D0 / D1 | Flat 40% / 45% on everything | Second jobs for higher earners |
| K codes | Adds untaxed income to your pay before taxing | Company benefits, tax owed from earlier years |
How much emergency tax actually costs
On £4,000 of monthly pay (£48,000 a year), the normal code takes about £591 of income tax. BR takes £800 and 0T about £972, because 0T gives no allowance and taxes pay above £3,142 a month at 40%, so a processing delay can cost £381 in a single month. The W1/M1 variant usually costs little in a steady job but bites when pay varies, because good months cannot be offset against quiet ones.
How to fix it
Give your new employer a P45 from the old job, or complete the starter checklist on day one. Then check your code in your HMRC personal tax account; employers should use the code HMRC sends them. Once the correct cumulative code is issued, your next payroll run recalculates the whole year to date and any overpayment comes back in that paycheck, with no claim form needed. If the year ends before it is fixed, HMRC settles it after April through a P800 calculation.
Second jobs are different
BR on a second job is often correct, not an emergency: your allowance is already used by the main job. What matters is the split. The two jobs calculator shows the combined position and when it is worth asking HMRC to split the allowance across both employments.
Frequently asked questions
Do I get emergency tax back automatically?
Within the same tax year, yes: the first payroll run on a cumulative code refunds it. After year end, HMRC reconciles and refunds through a P800 or your tax account.
How long does an emergency code last?
Usually one or two pay cycles once HMRC has your starter information. It does not expire by itself if the information never arrives, so chase the P45 or checklist.
Is my take-home wrong all year on W1/M1?
Only the months on the emergency basis differ. Compare any month against the UK salary calculator, which models the normal cumulative year.
Based on HMRC PAYE rules and the 2026/27 personal allowance of £12,570. Last updated 2026-11-04.