FA-72504 / Check-digit algorithms / Member archive

VIN transliterates S as 1 · case 04

VINs containing S get the wrong check digit.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

North American 17-character VIN check digit. Input must be 17 uppercase ASCII alphanumerics without I, O or Q (else "malformed"). Letters transliterate (A-H 1-8, J-N 1-5, P 7, R 9, S-Z 2-9); weights are 8,7,6,5,4,3,2,10,0,9,8,7,6,5,4,3,2 with weight 0 on the check position (9th). Remainder mod 11 is the check digit, 10 written X. Return [check character, whether position 9 matches].

Why this case matters

Vehicle registration and recall systems reject VINs with a bad check digit.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression ["5E80302J20HS0C2TB"]	`["3", false]`	`["X", false]`	Failed

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