On a subtly different tack, I've just been an taxed a car that's been off the road for about 18 months, and SORNed.
One of the questions on the V10 is "When did the last tax disc expire".
I dunno, offhand.
Apparently that MUST be filled out, else you can't have a new tax disc.
So - what happens if you've got a car that's been in a shed for a few years, and the old disc's long gone AWOL? Sure, if you've bought it off the road, you say when you got it - but what if you last used it about 10 years back, and have been restoring it?
What if you put the wrong answer (like I have - I guessed at Jan 03, but the woman behind the counter put Jan 04)?