FA-72575 / Check-digit algorithms / Member archive

MOD 11,10 starts the fold at one · case 05

Check digits disagree with the hybrid system for most payloads.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

ISO 7064 MOD 11,10 hybrid check digit generation for a nonempty ASCII digit payload (else None). Start with p = 10; for each digit p = ((p + d) mod 10, with 0 replaced by 10) * 2 mod 11; the check digit is (11 - p) mod 10.

Why this case matters

Tax and personal identification numbers (for example OIB-style identifiers) use the hybrid MOD 11,10 system.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression ["9795751"]	`9`	`6`	Failed

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