P45 provision to new employer when you haven't worked in years

I've a sticky situation that I'm hoping someone will have some input on. I haven't worked a steady job in 3 years but have a friend with an IT contracting company who has said they'll give me a reference and let me put it on my CV (I'm a Network Admin, MCSE on NT from years ago) As he's been so good so far, I don't want to pull the p*** and ask for a P45 as well for a fictional job.

What I need to know is what will happen if someone does offer me a job and I need to provide a P45. Can the tax office issue me one of the famous "amended" ones .. I've read other posts before submitting this and I see that it doesn't take a genius in payroll to roughly work it out by looking at PRSI credits, etc .. The OH has been claiming all my tax credits so I'm not sure where I stand.

Thx
Jaz

You don't need to provide a P45 for a new job, you just need to get the employer number of your new employer and ring the employee helpline, quoting your PPS and stating that you are working for the new employer. They will then issue a cert of tax credits to your new employer. If you OH is already claiming some tax credits for you, you will just get the remainder for your new job unless you reapportion some of it to yourself.

what exactly is the purpose of the p45, what do employers use it for, is just for tax and pay or is it to check employment history?

if you dont have a p45 you can just fill out a p46 cant you?