In the Republic of Ireland and the United Kingdom, the P45 is the form that a person is handed when leaving a job. The P45 details income for social security purposes. (The two countries' respective P45s are actually different; it's just that the UK and Ireland have very similar administrative processes here.)

Use of the term "P45" depends on context. See the following examples:
to be given your P45 -- to get fired (possibly unceremoniously)

to ask for your P45 -- to quit your job (possibly unceremoniously and/or defiantly)

to be in possession of your P45 -- to be jobless
(The P45 is handed to the employer when starting at the next job.)
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A smal room where 3 to 5 people engage in sexuel or semi-sexuel acts
Person 1:I participated in a p45 yesterday.
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Pragmatic notification by text, email, phone call to notify someone that their relationship with you is now at an end.
"Did you hear? Peter , the cowardly twunt, issued Linda with a relationship P45 by text!"
"Quick! Get the tissues. She's gonna blow!"
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To be fired in the manner of the 45th President of the United States being fired.
You've been P45'd!
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the smallest road legal car built by the top gear crew(James may,Richard Hammond,Jeremy Clarkson)
person 1: have you seen the peel p45

person 2: yes, i have
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When one is dismissed (sacked) from their employment in the UK
Person 1: Yo is Jason in today?

Person 2: Nah Bob P45'd him yesterday evening!
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