As most will know, the system changed on 1st October 2014. Having just done so myself and in the absence of sufficient information, I was unclear how to tax the vehicle at the time of purchase - particularly as it was a private purchase. It is quite straightforward however. As long as insurance is in place and a current MOT is in force, you can tax a vehicle 24/7 either by phone or on the internet using the 12 digit reference shown on the V5C/2 tear off section of the registration document. You can also do it at a post office which issues roadtax (not all of them do nowadays - all they do is scan the V5C - no application forms for registration documents etc etc as previously. The web address is: www.gov.uk/vehicletax The telephone number is 0300 123 4321 (Cost from a landline between 2p and 10p - from a mobile 10p to 40p) The vendor will automatically receive a refund of any unused tax.