A registration mark and a registration certificate are two halves of one system and they are not the same thing. The mark is an index number that can be moved between vehicles. The certificate is the document that says who is responsible for the vehicle and what the state believes the vehicle to be. Reading a used car's paperwork properly means knowing which of the two you are holding and what each can be made to hide.
What information is found on a vehicle registration document
The registration certificate carries the registration mark, the vehicle identification number, the make, the model, the colour, the engine number and capacity, the fuel type, the date of first registration, the number of former keepers, the date the current keeper acquired it, the taxation class and the emissions figure. It also carries the name and address of the registered keeper, which is the part that is personal data, and a document reference number used to authorise transactions.
A plate can move, and the record follows it
A registration mark can be retained, transferred to another vehicle or sold, through the DVLA retention and transfer services. When that happens the vehicle it left goes back to an age related mark, and anyone searching the old number will be looking at a different car. That is legitimate and common, and it is also the single easiest way to make a history look shorter than it is, which is why a serious check reads the VIN off the metal and asks whether the plate has changed.
Number plate history, and what is actually kept
The change of a registration mark is recorded against the vehicle, and a paid history check will report a previous registration and the date it changed. The plate itself carries no history you can look up: there is no public archive of every vehicle a mark has ever been on. If a seller has recently put a personalised plate on a car, ask what mark it carried before and run the check on that one as well as on the current one.
The plate itself has rules
The physical plate has to meet the legal requirements for character font, spacing, size and background, and the rules are enforced at the MOT. Non standard spacing that makes a mark read as a word, tinted or patterned backgrounds and unauthorised fonts are all failures, and they also make the car easier for automatic number plate recognition to misread. If you are buying a car with a personalised mark, look at the plate as well as the paperwork.
Questions people ask about car registration plate
Does the V5C show the previous registration number?
Not reliably. A paid history check reports a registration change and its date, which is the field to look for. The certificate itself shows the current mark.
Can I look up the history of a number plate?
No public archive lists every vehicle a mark has been on. What is available is the vehicle's own record, including whether its registration has changed and when.
Is the log book proof of ownership?
No. It records the registered keeper. A car on finance is owned by the lender while the keeper is somebody else entirely, which is why an outstanding finance check is a separate question.
What makes a number plate illegal?
Non standard character spacing, an unapproved font, a patterned or tinted background, or a plate that does not meet the required size and reflectivity. All of those fail an MOT.