What Is P45?
By PayMetric Labs Research Desk
Short answer
A P45 is the document your employer must give you when you leave a job, showing your pay and tax deducted for that employment in the current tax year.
When you leave a job, your employer is legally required to issue a P45. It has four parts: one goes to HMRC automatically, and you keep the rest to give to your new employer (or Jobcentre Plus if you're claiming benefits). It shows your tax code, total pay, and tax paid at that job in the current tax year up to your leaving date.
Handing your P45 to a new employer matters because it lets them apply the correct tax code from day one, rather than putting you on an emergency tax code that can overtax you until HMRC sorts it out. Without a P45, most new employers will ask you to complete a starter checklist instead.
If you lose your P45, you can't get a replacement copy from your old employer, HMRC doesn't issue duplicates either, but your new employer's starter checklist process handles this fine, and any overpaid tax gets corrected once HMRC updates your record.
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This glossary entry is for general information only and does not constitute financial, tax, or legal advice. Rates and thresholds shown reflect current published guidance and may change.