P45 /ˌpiː fɔːti ˈfaɪv $ -fɔːrti-/ BrE AmE noun
in the UK, an official document that is given to you by your employer when you leave a job. It gives details of the money you have earned and the taxes you have paid during this period of employment, and if you start a new job you have to give it to your new employer. People sometimes use the expression ‘get your P45’ when they mean ‘lose your job’.