http://www.direct.gov.uk/en/Motoring/OwningAVehicle/UntaxedVehicle/DG_4022058
Pretty ridiculous rule if you ask me, clearly aimed at catching people out.Recently registered as the vehicle keeper
If you have become the registered keeper of the vehicle and received your V5C during the current month you will need to fill in a V890 ‘Statutory Off Road Notification (SORN)’ form and send it to DVLA, Swansea SA99 1AR.
For example, if you became the keeper on 4 December and received the V5C on 26 December you will need to fill in a V890. If you became the keeper on 28 November and received the V5C on 20 December you could SORN online or by phone.