Buyer guide

Chassis number check: what it is and how to check one

On a modern car the chassis number and the VIN are the same 17 digits. Where to find it, how to read it, and what a chassis number can and cannot tell you about a used car.

Updated 20 August 2026

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The short answer

On anything built since 1981, the chassis number and the VIN are the same 17 character code, so a chassis number check and a VIN check are the same thing. Find it on the windscreen base, the driver door pillar or the logbook, check the car with it, and make sure the number on the car itself matches the number on the paperwork before you buy.

Chassis number and VIN are the same thing

Chassis number is the older name and it stuck, particularly in the UK and Ireland. Before standardisation, manufacturers stamped their own numbering onto the frame and each one did it differently. Since 1981 every car has carried a single 17 character VIN instead, and that is the number people are pointing at when they say chassis number today.

So if a form, an insurer or a seller asks for the chassis number, give them the VIN. On a genuinely old vehicle, built before the standard, a shorter frame number may be all that exists, and no online history check will cover it because there is no standard registry keyed to it.

Where to find the chassis number on the car

Five places, in the order most people find it fastest.

Base of the windscreen driver side, readable from outside through the glass. This is the one to check first because you can do it before anyone opens the car.
Driver door pillar a printed plate or sticker that shows when the door is open, usually alongside tyre pressures and the paint code.
Under the front seats or the carpet stamped straight into the floor pan on many cars, which is the version hardest to tamper with.
Engine bay on the manufacturer plate, often on the bulkhead or a suspension turret.
The paperwork the registration document, the insurance certificate and usually the service book carry it too.

Check the car against the paperwork, not one or the other

A number on the car that does not match the registration document is one of the clearest warning signs there is. So is a plate that looks disturbed, or a stamping that has been ground down and redone. These are among the very few problems you can catch with no tool and no report, just by looking in two places.

How to read the 17 digits

What each position means

Characters 1 to 3: manufacturer and country of build
Characters 4 to 9: model, body, engine and restraints
Character 10: the model year
Character 11: the assembly plant
Characters 12 to 17: the serial number for that one car

Reading it without mistakes

Always 17 characters, never more or fewer
The letters I, O and Q never appear in a VIN
So an apparent I or O is a misread 1 or 0
Photograph the plate rather than copying by hand
A shorter number means a car built before 1981

Misreading a 1 as an I is the single most common mistake when copying a chassis number off a dusty plate, and it is why a check comes back with nothing found more often than any other reason.

What a chassis number check can and cannot tell you

The number opens two different doors, and only one of them is free.

Decoding the number alone gives you the specification the car was built with, and that is free. To find out what has happened to the car since, the mileage recorded over time, damage and theft records, and which countries it has been registered in, the number has to be looked up in official registries, and that is what a history report does.

Enter the chassis number above and MrVIN shows a free preview of what was found for that car before you decide whether to buy the full report at EUR 19.90 to 24.90. If the car has a clean, thin record, you will see that too, which is worth knowing before you pay for anything.

MrVIN the bear checking a car's history report

Check the VIN before you buy

See the car's real mileage, damage and import history across 30+ countries, with a free preview of the findings before you pay.

Example: WBA3A5G59DNP26082Free preview included

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Frequently asked questions

Is the chassis number the same as the VIN?

On any car built since 1981, yes. Chassis number is simply the older name for the same 17 character VIN, and the two terms are used interchangeably in the UK and Ireland. Only on vehicles predating the standard is a separate, shorter frame number involved, and those fall outside every modern history database.

How many digits is a chassis number?

Seventeen characters, a mix of letters and numbers, with no I, O or Q anywhere in it. Anything shorter is either a pre 1981 frame number or a partial number that has been copied incorrectly, and a history check will not accept it.

Can I check a car history by chassis number for free?

You can decode the specification free of charge. The history itself, mileage readings, damage and theft records, comes from official and licensed sources that charge per lookup, so no service gives that away. MrVIN previews what was found for your chassis number at no cost, so you can see whether a full report is worth buying for that particular car.

What if the chassis number on the car does not match the documents?

Do not buy the car. A mismatch between the number stamped on the vehicle and the number on the registration document is one of the clearest warning signs there is, and it points to a cloned, stolen or illegally rebuilt vehicle. The same applies to a plate that looks tampered with or a stamping that has been ground and redone.

Where is the chassis number on a UK registered car?

In the same physical places as on any other car, the windscreen base, the driver door pillar and the engine bay plate, and on the paperwork it appears in section 4 of the V5C registration certificate. Check the car and the V5C against each other rather than relying on the document by itself.