P45
When your boss says you're no longer their employee, and it's usually because you did something stupid or you were bad at your job.
My boss said, 'You're fired. You're the worst employee I've ever had.' That was my P45.
I got a P45 because I forgot to turn on the coffee machine.
They handed me a P45 and said, 'You're fired. We're all better off now.'