What the check digit is
Position 9 of a VIN is a check digit on North American vehicles. Each of the other sixteen characters is converted to a number, multiplied by a fixed weight, and the total is divided by eleven. The remainder is the check digit, written as 0 to 9 or as X for ten. If you mistype one character, the arithmetic stops working and the error is caught.
It is an elegant mechanism and it is mandated only in North America and China. Everywhere else, whether a manufacturer computes a conforming digit is that manufacturer's own choice, and some of them use position 9 for something else entirely.
Who computes one and who does not
| Manufacturer | Position 9 outside North America | Can a typo be caught? |
|---|---|---|
| BMW and MINI | A genuine conforming check digit, computed voluntarily | Yes. Every sampled European BMW and MINI validates |
| Rolls-Royce | Not claimed by this decoder | No. No Rolls-Royce VIN has ever been checked, and a false alarm there is worse than silence |
| Mercedes-Benz | Part of the Baumuster, not a check digit | No. Of 21 sampled cars, 18 fail legitimately and 3 pass by coincidence |
| Nissan, export layout | The third character of the chassis code, the 1 in Y61 | No. Genuine export Nissans fail as a matter of course |
| Nissan, North American layout cars | A genuine check digit | Yes. Every harvested Gulf Patrol Y62 and India-built Sunny validates |
| Toyota, modern export | A genuine conforming check digit, computed voluntarily | Yes. 195 of 197 sampled VINs validate |
| Toyota, legacy scheme | Model data, part of the frame code | No |
| Porsche, rest of world | A literal Z, which is not even a legal check digit character | No. Validating would reject every genuine export Porsche |
| Tesla, all factories | A genuine check digit | Yes, at Shanghai and Berlin exactly as at Fremont |
This is why the answer has to be per manufacturer rather than per region. BMW and Mercedes are both German, both sell the same cars into the same markets, and they give opposite answers. A decoder that applies one European rule will either condemn every genuine Mercedes or throw away a free typo detector on every BMW.
What this decoder does about it
Where a manufacturer is known to compute a conforming digit, this decoder validates it and a failure is reported as a probable typing mistake, which is genuinely useful. Where a manufacturer does not, the field is reported as unknown rather than invalid. It is never guessed, and a failed check is never used to decide which VIN layout is being read, because an export VIN passes the test by chance roughly nine times in a hundred while a merely mistyped American VIN fails it every single time. The test tells you nothing reliable about the layout.
When a failure does matter
If your car is a BMW, a MINI, a modern Toyota, a Tesla, or any North American market vehicle, a failed check digit is worth taking seriously. Re-read the VIN from the registration card rather than from a listing or a photograph, and check the characters that are easiest to confuse. VINs never contain the letters I, O or Q, so any of those in a VIN you have been given is a transcription of a 1 or a 0.
Common questions
My VIN failed a check digit test. Is it fake?
Probably not. The check digit at position 9 is only mandated in North America and China. Outside those markets it is up to the manufacturer, and several use that position for something else. On an export Nissan it is part of the chassis code, on a Mercedes it is part of the Baumuster and on an export Porsche it is a literal Z. Genuine cars from all three fail the test routinely.
Which manufacturers compute a valid check digit outside North America?
BMW and MINI do, and every sampled European car from them validates. Toyota does on its modern export scheme, where 195 of 197 sampled VINs validate. Tesla does at every factory including Shanghai and Berlin. Mercedes-Benz does not, and neither does Nissan on its export layout or Porsche on its rest-of-world layout.
Check your own VIN
The free GCC spec check applies all of this to a single vehicle and shows the evidence behind its answer. The full VIN decoder returns every attribute it resolves, and the brand index has a page for each manufacturer scheme.