Emergency Tax Calculator UK

If your first payslip at a new job looks worryingly light, there's a decent chance you've been put on an emergency tax code. It's one of the most common payroll issues in the UK, it usually resolves itself, and in most cases any overpaid tax finds its way back to you automatically. But it helps to understand what's happened, how much extra you're paying, and what to do if it doesn't fix itself.

What an emergency tax code is

An emergency tax code is a temporary code your employer uses when they don't have enough information about your tax history to apply the right one, usually because HMRC hasn't yet told them what your correct code should be. Rather than not taxing you at all, the system applies a cautious default that often results in you paying more than you owe.

How to spot one on your payslip

For 2026/27, the standard tax code for most people is 1257L (S1257L in Scotland, C1257L in Wales). You're likely on an emergency or restrictive code if your payslip shows:

• 1257L W1, 1257L M1, or 1257L X — you get the standard allowance, but calculated per-period ("week 1 / month 1") rather than cumulatively, so overpayments from earlier in the year can't self-correct
• BR — all your income taxed at 20% basic rate, with no Personal Allowance at all
• 0T — no Personal Allowance, with tax charged across all bands as if you have no tax-free amount
• D0 or D1 — everything taxed at 40% or 45%, usually only correct for second jobs or high earners

How much extra you might be paying

The impact depends on the code. On a BR code, someone earning £2,500 a month who should have the full Personal Allowance is losing roughly £209.50 a month in extra tax, that's the 20% being charged on income that should be tax-free (£12,570 / 12 = £1,047.50 of tax-free pay each month). On a 0T code the effect can be larger still for higher earners, since higher-rate bands kick in sooner without the allowance. This calculator estimates the difference between what you're paying and what you should be. National Insurance is not changed by an emergency tax code; the code only changes how Income Tax is deducted.

Worked example

If you enter £2,500 as monthly gross pay and choose BR / basic rate, the calculator estimates £500 of emergency tax for that month. Under the standard 1257L allowance, the same monthly pay would usually have about £290.50 of Income Tax, so the estimated extra tax is £209.50. A Month 1 / Week 1 code can produce a different result because it gives a period allowance but does not correct earlier overpayments cumulatively.

For more detail, read our emergency tax refund calculator guide and guide to emergency tax codes.

Why it happens

The most common triggers:

• Starting a new job without a P45 — your new employer has no record of your pay and tax so far this year
• Moving from self-employment to employment — there's no P45 to hand over
• Taking on a second job — your allowance is usually allocated to your main job, leaving the second on BR
• Starting to receive company benefits — a company car or medical cover changes your tax position mid-year
• Receiving a pension for the first time — pension providers often apply an emergency code to a first withdrawal

How it gets fixed

In most cases, you don't need to do anything. When you start a new job, your employer submits a starter declaration to HMRC, and HMRC issues the correct code, usually within a few weeks. Because PAYE is cumulative, once the right code is applied, any tax you've overpaid so far in the year is automatically refunded through your next payslips.

If it doesn't correct itself after a couple of pay periods:

• Check your code and employment details in your personal tax account on gov.uk
• Contact HMRC to confirm they have your current employment on record
• If you've left a job mid-year and aren't working, you may be able to claim an in-year refund directly from HMRC rather than waiting

Emergency tax on pension withdrawals

A special case worth knowing: the first flexible withdrawal from a pension pot is very often taxed on an emergency month 1 basis, which can result in a substantial overpayment on large withdrawals. HMRC has forms for reclaiming this in-year rather than waiting until the tax year ends.

This is general guidance, not financial advice. For your specific tax code and any refund owed, check your personal tax account on gov.uk or contact HMRC directly.