I've got a car up for sale and wanted to tax it, but don't currently have any insurance on it. I can get a one day policy with a downloadable certificate easily enough for a few quid, but do they accept them at the post offices if the vehicle is only insured for the day on which you get the licence?
I seem to remember someone somewhere saying something about the car has to be taxed for a minimum duration (e.g. 28 days or something)...