The ninth character of a North American VIN is not descriptive. It is a checksum computed from the other sixteen characters using a fixed weighting, and its only job is to reveal mistakes.
Because the value is derived, a VIN with a single wrong or transposed character will almost always fail the check. That makes it a fast first filter on whether a number was copied correctly.
A failed check digit usually means a typing error. Occasionally it means someone invented a VIN, which is a much more serious matter.
Why it matters
If a VIN fails its own checksum, nothing else you do with it is reliable. Fix the number before drawing any conclusion.
How to check it
Any decoder validates the check digit automatically. If the seller's paperwork carries a VIN that fails, ask to photograph the plate on the vehicle itself.
Does this apply to the car you are looking at?
Run the VIN or plate and see what is actually on record.
Related terms
Definitions are general guidance, not legal advice. Title rules, total loss thresholds and inspection requirements are set by each state and change over time, so confirm the position with the motor vehicle agency for the state the vehicle is titled in before relying on it.