FA-72790 / Check-digit algorithms / Member archive

NRIC pairs the wrong series with each letter table · case 05

Either citizen or foreigner numbers get check letters from the other table.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Singapore-style NRIC/FIN check letter for the S, T, F and G series: nine characters, series letter, seven digits, check letter (else "malformed"). Weights 2,7,6,5,4,3,2; add 4 for T and G; r = sum mod 11; the letter is "JZIHGFEDCBA"[r] for S/T and "XWUTRQPNMLK"[r] for F/G. Return [expected letter, match].

Why this case matters

Identity verification forms validate NRIC/FIN numbers before submission.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression ["F5183813A"]	`["J", false]`	`["X", false]`	Failed

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