Technical Reference: Card Number Structure & Standards

Identification and processing of payment cards are governed by international standards that ensure interoperability between banks, networks, and merchants. This guide covers the core components of the Primary Account Number (PAN).

1. ISO/IEC 7812 Standard

The ISO/IEC 7812 standard regulates the numbering system for all identification cards used in international exchange. A standard card number (PAN) consists of three main parts:

2. Major Industry Identifier (MII)

The first digit of the IIN is the MII, which indicates the primary industry of the card issuer:

3. Luhn Algorithm (Mod 10)

The Luhn algorithm is a simple checksum formula used to validate card numbers against accidental errors (typos). It is not a security feature, but a data integrity tool.

def is_luhn_valid(card_number):
    digits = [int(d) for d in str(card_number)]
    checksum = 0
    reverse_digits = digits[::-1]
    
    for i, digit in enumerate(reverse_digits):
        if i % 2 == 1:
            digit *= 2
            if digit > 9:
                digit -= 9
        checksum += digit
        
    return checksum % 10 == 0