Emergency tax codes and how to fix them

What tax code should I be on?

For most people with one job, no taxable benefits and no tax owed from earlier years, the answer for 2026/27 is 1257L. It gives you the full personal allowance of £12,570 spread evenly across the year. A Scottish taxpayer has the same code prefixed with S, and a Welsh taxpayer with C. If yours differs from that and you cannot explain why, it is worth an hour of your attention: the personal allowance guide lists the legitimate reasons for a different code, and anything outside that list is likely an error.

What the emergency codes do

Each of those codes has its own page with a full worked example: BR, 0T, D0 and 1257L M1.

What does W1, M1 or X actually change?

Normal PAYE is cumulative: every payday, payroll looks at your total pay and total tax for the year so far and corrects any imbalance. That self-healing is what makes the system work across pay rises, bonuses and gaps in employment. A W1, M1 or X marker switches it off. Each period is then treated as if it were the only one in the year, with one twelfth of your allowance and one twelfth of each band, and nothing is ever recalculated. If you started part way through the year, that means the allowance for the months you did not work is simply never given to you, which is where most overpayments come from.

Why am I on an emergency code?

• You started a new job and your employer did not get a P45 in time.
• It is your first job, or your first after a period out of work or study.
• You started a second job, so the allowance is already used by the first.
• You began drawing a pension, or took a taxable lump sum from one.
• You moved from self-employment into PAYE.
• Your circumstances changed, for example a company car started or ended.

How do I fix it and get the money back?

1. Give your employer what they need. A P45 from the previous job, or a completed starter checklist if you do not have one. This alone resolves most cases within a pay period or two.
2. Check your HMRC personal tax account. You can see the income HMRC thinks you have and correct it there, which is usually faster than phoning.
3. Wait one payday. Once a cumulative code is issued, the refund normally arrives automatically through payroll: your next payslip shows a smaller tax figure, sometimes a negative one.
4. If the tax year has ended, HMRC reconciles automatically and issues a P800 calculation with the repayment. You can also claim directly, and claims can go back four tax years. The tax refund calculator estimates the amount first.

Being on an emergency code does not mean you have done anything wrong, and it does not mean the money is lost. Income tax is reconciled across the whole tax year, so an overpayment in month three is normally corrected by month five, or repaid after April at the latest. National Insurance is the exception, because it is charged per pay period and never reconciled annually, which is why a one-off bonus can cost NI that you genuinely cannot reclaim.

Related guides

All 10 guides are listed on the guides index, and every calculator on the home page.