THE QUICK ANSWER
Compare the vehicle identification number on the car with its registration and supporting documents. Ask a qualified professional to investigate mismatches or signs of alteration. Decoding a VIN’s format does not prove a vehicle’s identity, ownership or history.
Find the identifiers on the actual vehicle
Use the manufacturer’s information to locate the vehicle identification markings. Depending on the vehicle, there may be a visible identifier near the windscreen and other markings elsewhere. Have an inspector help if access or interpretation is uncertain.
Read the characters carefully. A photograph can make comparison easier, but the comparison should relate to the vehicle in front of you rather than only an image in an advert.
Compare documents and records
Check that the identifiers agree across the car, registration documents, service invoices and any history report. A report about another vehicle is of little value even if its make, model and colour look similar.
For an import, ask for the earlier registration documents and check the chain of identifiers. Keep a note of anything missing so it can be resolved before payment.
Understand the difference between decoding and checking
A decoder interprets a code. A history search queries records associated with identifiers. A physical inspection helps establish what is actually present on the car. These are different tasks, and none should be silently substituted for another.
Our registration tool explains a modern Irish plate’s format only. It cannot establish a VIN, a make or model, or a link between a plate and a particular car.
Pause when something does not match
Ask for a documented explanation rather than accepting that a mismatch is “just an admin issue”. Repairs, replacement components and record errors need appropriate evidence; suspected alteration needs professional investigation.
If the seller cannot resolve an identity concern, do not let a favourable price push you into the purchase. You need to know which vehicle you are buying before interpreting the rest of its history.
Sources & further reading
Public resources consulted for this guide. Links and availability can change. Checked 19 October 2026.
- GOV.UK: checks when buying a used car
Vehicle identity, documents and MOT checks for UK vehicles.
- RSA: buying and selling a vehicle
Road Safety Authority advice, including independent vehicle inspections.
- Cartell: car-check help and limitations
Explains limitations, including Irish stolen-vehicle file access.
Our guides explain a buying process; they do not determine a particular vehicle’s condition or your legal position. Read our editorial policy.