EMERGENCY TAX · 2026/27
Emergency tax calculator
Estimate what a temporary tax code could do to one month’s pay and compare it with 1257L. This is most useful when a new job, starter form or HMRC update has pushed a pay packet into emergency treatment.
Estimated monthly take-home
- Estimated Income Tax
- £652
- Estimated employee NI
- £172
- Tax difference vs 1257L
- +£221
This annualises one month to illustrate the code. Week 1/Month 1 payroll can differ because each pay period is calculated independently.
What this calculator does
It estimates the short-term effect of a temporary PAYE code on one payslip and compares it with a standard cumulative code. That helps users see whether the current month looks wrong because of the code, the pay period or a genuine tax issue.
Worked example
Emergency codes can make the first payslip look far lower than expected, especially when the Personal Allowance has not yet been applied. Once payroll receives the right information, later payslips may correct the position and recover some of the difference.
Why the result can differ
The impact depends on whether the code is W1, M1, X, BR or 0T, and on whether the payroll is using a cumulative or non-cumulative basis. The monthly result is only a temporary snapshot, not the final tax year position.
SOURCES & REVIEW
Checked against official guidance
Last reviewed 1 September 2026 · Rule version GB-2026.27.1
Daily/weekly source monitoring. If a source changes, the affected rule set is reviewed before publication.
All source links are kept visible so you can verify the figures used on this page.
GOV.UK: Emergency tax codes ↗GOV.UK: Check your Income Tax ↗Sources, methodology and update policy →Report an issue or correction →WHY RESULTS DIFFER
Why two users can see different results
Why the result can differ
Different tax codes, payroll periods, Scottish bands, pension methods or lender assumptions can change the outcome.
One-off bonuses, pay frequency, overpayments, allowances and reliefs can move the result away from a simple annual estimate.
Where a rule depends on eligibility or legal status, this page shows an estimate and links to official guidance.
This section is intentionally repeated on key tools so the explanation stays near the result instead of being hidden in a separate policy page.
COMMON QUESTIONS
Frequently asked questions
What does an emergency tax code look like?
Emergency treatment may show W1, M1 or X after a code. 0T can also be used when payroll lacks allowance information.
Will emergency tax be refunded automatically?
Payroll may correct it after HMRC supplies a cumulative code; otherwise HMRC may reconcile the year.
Is 1257L always the fix?
Not always. The correct code depends on the taxpayer’s current circumstances.