What Is a P45?

When you leave a job in the UK, your employer hands you a form that quietly does a lot of work: the P45. It is one of those documents people receive, file away, and never really read — until they start a new job and discover it matters. Get it to your next employer promptly and your tax should carry over smoothly; lose it or forget it, and you can end up overpaying for weeks. This guide explains what a P45 is, what it contains, why it matters, and what to do if it goes missing. This is general information, not financial advice.

What a P45 is

A P45 is the form an employer gives you when you stop working for them, summarising your pay and the tax deducted so far in the current tax year. Its formal name is "Details of employee leaving work", and it exists to make sure your tax position travels with you from one job to the next under PAYE.

The UK tax year runs from 6 April to 5 April, and your tax-free Personal Allowance is spread across it. When you change jobs mid-year, your new employer needs to know how much you have already earned and how much tax you have already paid, so they can pick up where the last employer left off. The P45 carries exactly that information.

A P45 is a handover document. It tells your next employer where your tax stands so the year continues smoothly instead of restarting from scratch.

What a P45 contains

A P45 is short but information-dense. The key details include:

• Your total pay in the current tax year up to your leaving date.
• The total Income Tax deducted in that period.
• Your tax code at the time you left.
• Your National Insurance number and your employer's PAYE reference.
• Your leaving date.

The form comes in several parts. One part goes to HMRC automatically; the others are for you to keep and to give to your next employer or, in some cases, a benefits office. You do not need to memorise which part is which — the form is labelled — but you do need to hold on to it.

Why your P45 matters

The P45 matters most at the moment you start a new job. Hand the relevant parts to your new employer and they can apply the correct tax code straight away, continuing your allowance and tax record for the year. Without it, they have to make assumptions.

Those assumptions often mean an emergency tax code. As our guide to emergency tax explains, these codes can ignore part of your allowance and tax each pay period in isolation, so you may temporarily pay too much. The position usually corrects itself once HMRC has your details, and any overpayment can come back as a refund — but giving your new employer the P45 promptly avoids the hassle in the first place.

A P45 can also matter if you:

• Claim certain benefits after leaving work, where the office may ask for it.
• Take money from a pension, where the provider uses it to apply the right tax.
• Need to check or query your tax, since it is a clear record of your pay and tax to date.

What to do if you lose your P45

This is the question people most often ask, and the answer surprises them: there is no replacement P45. Employers are not able to issue a duplicate. If you have lost yours, do not panic — there is a standard fallback.

Your new employer will ask you to complete a starter checklist (which replaced the old P46). This is a short form about your circumstances — for example, whether this is your only job — that lets the employer work out a sensible temporary tax code until HMRC confirms the right one. The process is routine, and payroll teams handle it all the time.

To keep your tax accurate while things settle:

1. Complete the starter checklist honestly and promptly.
2. Check your first payslip to see what tax code has been applied.
3. Use your Personal Tax Account on GOV.UK to confirm your details, and contact HMRC if something looks wrong.

If a wrong code means you overpay, you can reclaim it, so a lost P45 is an inconvenience rather than a disaster. Citizens Advice offers free guidance if you are unsure what to do after leaving a job.

P45 versus P60 and P11D

It is easy to muddle the PAYE forms, because they look similar and all relate to your pay. The distinction is really about timing and purpose:

• A P45 is given when you leave a job and covers the tax year up to your leaving date.
• A P60 is given at the end of the tax year by your current employer and summarises your total pay and tax for that whole year — useful for proving income or completing a Self Assessment return.
• A P11D reports taxable benefits in kind, such as a company car or medical insurance, and is explained in our guide to the P11D.

Keeping all three safe is sensible: together they form a clear record of your earnings, tax and benefits, which is invaluable if you ever need to prove income or query a tax calculation.

The bottom line

A P45 is the form you receive when you leave a job, showing your pay and tax for the current tax year so your next employer can apply the right tax code and avoid an emergency one. Give the relevant parts to a new employer promptly, and keep a copy for your records, because it is also useful for benefits, pensions and tax queries. If you lose it, there is no duplicate — you simply complete a starter checklist instead — and any overpaid tax can be reclaimed. To check your tax is right, use your Personal Tax Account on GOV.UK.