How to check your tax code when changing jobs

Katerina Galkina · EN · 07/10/2026

Compare paperwork from both employers

Request your P45 when leaving and give it to your new employer. If it is unavailable, complete the starter checklist accurately, including information about other employment. Do not guess an answer to obtain a lower deduction: that can create a later underpayment.

Keep your final payslip from the old job and the first from the new one. Compare payment dates, taxable pay, Income Tax and tax code. Distinguish gross pay, take-home pay and cumulative figures for the tax year. A bonus, holiday payment or payments from both employers in the same period can affect the result.

Check the details HMRC holds

Your employer uses your tax code ↗ to calculate deductions. Each employment or pension can have its own code. A colleague’s code is not a template for yours: other income, allowances and adjustments matter.

In Check your Income Tax ↗, check that the old employment has ended, the new one appears and estimated income and company benefits are correct. If you genuinely have two jobs, do not remove one merely because it looks duplicated. Correct specific errors and save confirmation.

Understand an emergency code

HMRC identifies ↗ W1, M1, X and NONCUM as emergency-basis indicators. Tax is calculated using the individual pay period rather than the normal cumulative approach. This is often temporary while information arrives from the employers.

Give payroll any missing P45. HMRC says an update after starting a job can take up to 35 days. If the problem continues, follow the tax-code correction process ↗. Contact payroll immediately about an obvious payroll calculation error: correcting HMRC records and correcting a payslip are connected but distinct tasks.

Check that the correction reaches payroll

After receiving a new-code notification, check that your employer has received it and review subsequent payslips. Do not assume a refund will arrive on a particular date: the process depends on the reason for the change and calculation method. If too little tax was deducted, reserve money until the position is reconciled.

Changing jobs alone does not mean you must complete Self Assessment. Check other possible filing reasons separately, including self-employment and overseas income. Retain P45s, P60s and HMRC messages. The official tax-code service does not require a paid intermediary.