There used to be an offence of failure to display a disc but since ANPR/databases/internet tax renewal the offence had been changed to failure to possess.
As long as the tax is logged as current the car is legal to drive.
Do I read that correctly? Does that mean I don't have to display my tax-disc now? I got 'done' a few years ago for 'Not possessing' AND 'Not displaying' Expensive lesson learned!
As an aside to this I've just taxed the car on-line. From opening up Google to getting to the 'Payment accepted' page took 3 minutes and 13 seconds!!! So much less hassle than finding all your documents and traipsing down to the Post Office and waiting in line behind folk posting 15 eBay parcels and arguing about the price!!!