Key takeaways
- Emergency tax on a £35,000 salary costs £209.50 a month, because the code gives you no personal allowance at all — it is temporary, and the money comes back.
- 0T gives you no personal allowance at all; BR taxes all of your pay at a flat 20% with no allowance; Week 1 / Month 1 taxes each pay period in isolation.
- Give your employer your P45, or complete a starter checklist — HMRC usually corrects the code automatically once they have your details.
- Emergency tax is not a fine, and it is not lost money — it is tax paid early, under a code that assumes the worst.
Emergency tax on a £35,000 salary costs £209.50 a month — your take-home falls from £2,297.43 to £2,087.93 — because the code gives you no personal allowance at all. It is temporary, and the money comes back.
You start a new job, you work a full month, and the payslip is wrong. Not a little wrong — hundreds of pounds wrong. The tax line is far too big, the take-home is far too small, and nobody in payroll seems surprised. What has happened is almost always the same thing: an emergency tax code. This article explains what it is, what it costs you, and how to get the money back.
What an emergency tax code is
Your tax code tells your employer how much of your pay is tax-free. The normal code for most people is 1257L, which means a £12,570 personal allowance. But your employer can only use that code if HMRC has told them to — which happens when they receive your P45 from your previous job, or the starter checklist you filled in when you joined. If neither has arrived by payday, HMRC instructs your employer to use an emergency code instead.
Emergency codes come in two main forms. The first is 0T, which gives you no personal allowance at all: your whole taxable pay is taxed, at 20% up to the basic-rate limit and 40% above it. The second is BR, which taxes all of your pay at a flat 20% with no allowance. There is also a Week 1 / Month 1 basis, which means the tax is worked out on that pay period alone, with no memory of what you earned earlier in the year. All three have the same effect: too much tax, taken too soon.
What it costs: £35,000 worked out
On a £35,000 salary with the usual auto-enrolment pension, the correct code (1257L) gives you £4,198.40 of income tax a year and take-home pay of £27,569.20 a year — £2,297.43 a month. On an emergency code the picture is very different.
| Tax code | Income tax / year | Take-home / year | Take-home / month | Cost vs 1257L / month |
|---|---|---|---|---|
| 1257L (correct) | £4,198.40 | £27,569.20 | £2,297.43 | — |
| 0T (emergency) | £6,712.40 | £25,055.20 | £2,087.93 | £209.50 |
| BR (emergency) | £6,712.40 | £25,055.20 | £2,087.93 | £209.50 |
| K100 | £6,912.40 | £24,855.20 | £2,071.27 | £226.16 |
The £209.50 a month is simply the tax on the missing £12,570 personal allowance: £12,570 × 20% is £2,514.00 a year, or £209.50 a month.
The emergency codes cost exactly the same at this salary — £6,712.40 of tax — because all £33,562 of taxable pay sits inside the 20% basic-rate band either way. 0T taxes it band by band; BR taxes it flat at 20%; at this salary the two methods agree. A K code is worse still: K100 adds £1,000 to your taxable pay, so the tax rises to £6,912.40 and take-home falls to £2,071.27 a month.
At higher salaries the emergency codes diverge. Once your pay crosses into the 40% band, 0T taxes the top slice at 40% while BR keeps charging 20% — so BR becomes the cheaper mistake, and 0T the expensive one. Either way, the fix is the same: get the right code on the record.
Week 1 / Month 1: the other half of the problem
Emergency codes often arrive with a Week 1 or Month 1 basis attached. Normally PAYE is cumulative: each month, your employer looks at everything you have earned so far this tax year and works out the tax due on the total. Week 1 / Month 1 switches that off. Each pay period is taxed in isolation, as if it were the first period of the year, with one twelfth of your allowance and no memory of earlier months.
On a steady salary this makes little difference. But if you had earlier pay in the same tax year — from a previous job, or a bonus — the cumulative system would have used your unused allowance from those months. Week 1 / Month 1 cannot see it, so it taxes you as if the allowance starts again. The result is the same shape as the emergency code itself: too much tax now, corrected later.
How to fix it
Step one: give your employer what they need. If you have a P45 from your last job, hand it in — it carries your tax code and your year-to-date pay and tax, which is everything payroll needs. If you do not have one, complete a starter checklist (the form that replaced the P46). It asks three questions: whether this is your only job, whether you have another job or pension, and whether you have a student loan. Answer them carefully, because the wrong answer puts you on the wrong code in the other direction.
Step two: wait for HMRC. Once your employer has your details, they send them to HMRC, and HMRC issues a new tax code — usually within a few weeks. Your employer applies it, and the cumulative system does the rest: it recalculates your tax for the whole year so far and refunds the overpayment through your next payslips. You do not usually need to claim anything. If the tax year ends and you are still owed money, HMRC reconciles it automatically and either repays you or adjusts your next year's code — you can also check your position in your Personal Tax Account on GOV.UK.
Step three, if it drags on: call HMRC or check your Personal Tax Account yourself. Your tax code is visible there, along with the reason for it. If the code is wrong for a reason you can see — a previous employment HMRC still thinks you have, for example — you can tell them, and they can fix it while you are on the phone. Do not wait until April. Emergency tax is designed to be temporary; a code that stays wrong for a year is a code nobody has looked at.
When it is not an emergency code
Not every low first payslip is an emergency code. Sometimes the tax is right and the problem is elsewhere: a pension deduction that started immediately, a student loan that should not be there, or a salary that was agreed monthly but paid four-weekly. Check the tax code line first — it is printed on every payslip. If it says 1257L (or S1257L in Scotland) and the numbers still look wrong, work through the payslip line by line: gross pay, pension, taxable pay, tax, National Insurance. The error is usually visible once you know what each line should be.
And one reassurance: emergency tax is not a fine, and it is not lost money. It is tax paid early, under a code that assumes the worst. Once the right code arrives, the system gives it back. The cost is cash flow — £209.50 a month on a £35,000 salary — and the fix is paperwork. Get the paperwork in, and the money follows.
Check your code against the calculator
Put your salary and tax code into the take-home pay calculator — it handles 1257L, BR, D0, D1, 0T, NT and K codes — and compare the result with your payslip. If the code is the problem, read How to read your payslip, line by line next, and the 2026/27 rates behind every figure on this page.
Questions
Why is my first payslip taxed so much?
Usually an emergency tax code. If your employer did not have your P45 or a starter checklist when you started, HMRC puts you on a code like 0T or BR that gives you no personal allowance. On £35,000 that costs £209.50 a month until the right code arrives.
How do I fix an emergency tax code?
Give your employer your P45 from your last job, or complete a starter checklist (formerly P46) so they can put you on the right code. HMRC usually corrects it automatically once they have your details — and any tax you overpaid comes back through later payslips or a repayment.
What does Week 1 / Month 1 mean on my tax code?
It means your tax is worked out on that pay period alone, with no memory of earlier months. It is used when HMRC does not yet know your year-to-date figures. Once your code becomes cumulative, the system catches up and refunds any overpayment automatically.
Get the money back
Emergency tax is tax paid early, under a code that assumes the worst. Once the right code arrives, the system gives it back — put your salary and tax code into the calculator and compare the result with your payslip.
Figures are for tax year 2026/27, England, Wales or Northern Ireland, auto-enrolment pension at 5% of qualifying earnings, no student loan. Rates: GOV.UK — last checked 5 November 2026. This site is not affiliated with HMRC or GOV.UK. Figures are estimates for guidance, not financial advice.