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Luhn Algorithm

The mod-10 check digit from ISO/IEC 7812-1. Works on any decimal string, not just a PAN — ARNs, RRNs and in-house reference numbers use the same scheme. Validate a number, compute the check digit for one that has none, or generate valid numbers for test data. Nothing is sent anywhere.

Spaces and dashes are ignored. Two or more lines are checked as a batch.

Results appear here

A Luhn check catches single-digit typos and most transpositions. It says nothing about whether a number was ever issued, is active, or belongs to anyone — a made-up number can pass, and a real one that fails was simply mistyped.