What matters
- For VINs governed by current U.S. 49 CFR Part 565, position 9 is a weighted modulo-11 check digit.
- The allowed U.S. character set excludes I, O, and Q, and a remainder of 10 is represented by X.
- A matching digit checks transcription consistency; it does not authenticate the physical vehicle, ownership, title, or documents.
Why this question matters
A useful vehicle database distinguishes standardized VIN data, manufacturer production records, enthusiast shorthand, recall campaigns, and the physical vehicle as it exists today.
What the evidence supports
Current 49 CFR Part 565 defines a check digit as a number or X used to verify VIN transcription, requires it in position 9 for covered VINs, publishes the letter values and position weights, and supplies a worked example. NHTSA’s certification FAQ describes manufacturer reporting of incorrectly assigned VINs to the federal VIN error database. vPIC supplies manufacturer-submitted decoding data but does not turn the checksum into an identity guarantee.
Start with the regulatory scope and allowed characters
Part 565 applies to specified vehicles and model-year ranges under U.S. regulation. For covered current VINs, the identifier contains 17 characters and position 9 is the check digit. The allowed letters are A–H, J–N, P, R–Z plus digits 0–9; I, O, and Q are omitted to reduce visual confusion with 1 and 0.
Do not reject every foreign-market identifier because position 9 fails the U.S. rule. An original manufacturer’s non-U.S. VIN, an older vehicle, or a regulated substitute label can involve different applicability. First establish the market, model year, and identifier type; then apply the correct rule. The TunerBench result should be labeled as a U.S. Part 565 check, not universal global authentication.
Calculate the position-9 character step by step
Keep numeric characters at their numeric values. Transliterate letters using the regulation’s table: A through H map to 1 through 8; J through N restart at 1 through 5; P is 7, R is 9, and S through Z follow 2 through 9. Multiply positions 1–8 by weights 8, 7, 6, 5, 4, 3, 2, 10. Position 9 has weight zero because it is the result being checked. Positions 10–17 use 9, 8, 7, 6, 5, 4, 3, 2.
Add all 17 products and divide by 11. The numerical remainder 0 through 9 becomes the digit; remainder 10 becomes X. The current eCFR worked example leaves position 9 blank in 1G4AH59H?5G118341, obtains a product sum of 411, and yields remainder 4—so the completed VIN uses 4 in position 9.
Use the checksum as one identity-control layer
A mismatch is useful evidence of a mistyped, misread, incorrectly assigned, or out-of-scope identifier. Recheck characters that are visually similar, compare every position with the dashboard plate, certification label, title and registration, and use the exact VIN for NHTSA decoding and recall lookup. NHTSA describes a manufacturer-led process for reporting assignment errors and normally supplying the owner with a letter identifying the erroneous and intended VIN. Contact the manufacturer about an assignment error rather than silently “fixing” an official record.
A match is much narrower evidence: the characters satisfy one arithmetic consistency rule. A copied VIN, substituted plate, cloned listing, or altered document can carry a mathematically valid number. The check also cannot prove mileage, lien or title status, ownership, installed equipment, or recall completion. Escalate discrepancies through the manufacturer, relevant DMV or title authority, law enforcement, or a qualified inspection process as appropriate.
For the regulation’s sample 1G4AH59H?5G118341, the weighted products total 411. Dividing by 11 leaves remainder 4, so position 9 must be 4. This validates the transcription rule only; it does not authenticate a particular vehicle carrying that VIN.
Illustrative example, not a measured vehicle test.
A repeatable workflow
- Confirm that the identifier is a 17-character VIN within the U.S. Part 565 rule being tested.
- Normalize case without guessing characters, then apply the official transliteration values and weights.
- Sum the products, take the remainder modulo 11, translate 10 to X, and compare position 9.
- Compare all physical labels and records, decode through NHTSA, check recalls, and escalate unexplained discrepancies rather than rewriting the VIN.
Where the shortcut breaks
A matching check digit is not proof of vehicle, plate, document, title, ownership, mileage, or seller legitimacy. A mismatch may be a transcription error, an incorrect VIN, or an identifier outside the rule’s applicability. This is an educational verification aid, not a title or fraud determination.
Sources and update method
TunerBench prefers government, standards-body, and component-manufacturer documentation. This guide is reviewed against the sources below and should be revisited when regulations, product data, or vehicle technology changes.