Even on a pension you still get P60s. I used to file all mine, from the various jobs I've had, still got them, though I've got rid of all the pay slips I used to keep. Looking at them sometimes I wonder how on earth I managed to live on that, going back to the '70s. It's like looking at ancient parish records. "For maintaining the churchyard and preventing the goats from wandering, to John Bonyfingers, one Groat per year" or some such.
They symbolise all those years of getting up, going to work, paying bills, going to bed knackered so you could do the same again merging together as you look back. It's said that people validate their identity and sense of self through work, and are likely to kick the bucket once retirement comes but even though I mostly enjoyed work, I just don't miss it.