When buying a second hand vehicle is always a bit risky if you aren't provided with the vehicles previous details such as service history. Each car once produced is provided with a Vehicle Identification Number (VIN) this is one way of checking the cars authenticity, although there are many more ways to check the authenticity of the vehicle.
Some things you can do to check the car is legal for road use, and also making sure it's not stolen are:
The mileage clock
This is the most common thing to be changed on second hand vehicles and if done can increase the asking price by hundreds of pounds if not thousands. This is usually done by private sellers, however, that's not to say dealers have never been known to do this. If you know what to look for you should be able to spot anything a bit suspicious. Some tell tale signs that the clock has been tampered with are; un-aligned numbers - if the numbers on the odometer are not lined up properly this could be a big give away, however, it's not entirely reliable as the numbers can be un-aligned for other reasons. This should still make you take caution so check the service history the garage that carried out the work should be listed in there and maybe even the odometer reading from the latest service, you could phone the garage to check the authenticity of this as service history forms can be forged. If in the service history it has the odometer readings check the continuity of how much the mileage goes up, how long it's been since the last service and what the mileage is now.
Car data check
This saves you a lot of hassle if anything does come up once you have bought the car. It means you give the VIN and other details of the car to a company that deals with this kind of work they will then go and find out whether the car is stolen, been written off before or still has finance left on it to pay. Some of these things you could be liable to pay even if you didn't know about the problem before buying, if done through a specialist company you can take out insurance so if they do miss anything on their check you don't have to pay any of the charges.
This is where plates have been copied off a genuine vehicle but it's either been stolen, written off and this could cause trouble with the police even if you are found to own a vehicle with forged plates. It is this kind of problem that is found by companies that check the car history for you so if you don't have the facilities to do these checks your self it's advised you get a company that can do them for you.
With there being more ways for people to hide the fact a vehicle is stolen it is more important than ever for you to check second hand vehicles history before purchasing it.