years ago the understanding (erroneus or not) was that they wouldn't 'do' you for 14 days.
We forgot to renew, (no reminders back then) and OH was stopped on the way to work (it was about 2 weeks into the month). Came home for his papers and rushed into town to get one at the main post office. But forgot to look at how long he could park in that space, and came back to find a ticket.
Ended up fined once for not having it (in the morning), then again for not displaying it (by the traffic warden, although he'd bought it by then), and a parking fine.
Grrr