A P45 is a document that your employer has to give you when you’re leaving your job.

It shows how much tax they deducted from your salary for that year and what your final tax code was.

The document is made up of four parts: 

• Part 1: This part is sent to HMRC
• Part 1A: This is yours to keep for your own records
• Parts 2 & 3: This is what you give to your employer when you start a new job, or to the Jobcentre if you’re out of work

Why is a P45 so important?

A P45 is important because it ensures you’re put on the correct tax code when changing jobs. If you don’t supply your employer with this in time, you could end up paying too much tax. Or you could be put on an emergency tax code. 

It’s also important if you’re self-employed, as you may need it when filing a Self Assessment tax return. If you’re unemployed and out of work, you’ll need a P45 to claim tax refunds on social welfare benefits from Jobcentre Plus. 

How long is it valid for?

A P45 is only valid for the tax year in which it was issued by HMRC. However, it’s worth storing it for at least 22 months after its validity has expired, like you would most tax records. Why? Well, HMRC can carry out income tax investigations for up to twenty years, so keeping records of your tax and documents like a P45 can help. 

If you’ve been unemployed for more than a year, your P45 won’t be valid if you start a new job. That means you might need to fill out a ‘Starter Checklist.’

What to do if you’ve lost your P45

Unfortunately, if you’ve lost your P45 you can’t get a replacement. This means that when you start a new job, you’ll be asked to fill in a new ‘Starter Checklist.’ HMRC should be able to calculate your new tax code from the details you give on this form, but it’s always worth checking that you haven’t been put on an emergency tax code.