This link will help clarify the law regarding selling a plate from a car.
http://www.direct.gov.uk/en/Motoring/Pe ... DG_4022576
It definately HAS! to have a current MOT, and as long as the tax didnt run out more than 1 yr previous and it was then put on sorn straight away,that should be fine.
If the car has been laid up in a garage or suchlike for XX amount of years then it will have to pass an mot,then be insured and then taxed in order for the plate to be sold.
And possibly inspected to see it is legit!!
Also look on the special notes, "front page bottom sec 3 blue" on the V5C to make sure it doesnt say non transferable,as it may have had its original plate removed years ago and a non transferable one issued by the dvla.
If you contact the help desk in the link,you can ask them," I am thinking of buying this number is it transferable??"
Go here and do a check to see when its last tax expired,,ie date of liability.
http://www.taxdisc.direct.gov.uk/EvlPor ... le+Enquiry
Good luck,I hope the car is not a basket case if it needs to get workerd on for an mot,if it is past it,the plate is worthless and will be scrapped with the car.