maximum of 12 digits when used in conjunction with a six digit IIN. When using an eight digit IIN, the maximum total length of the primary account number (PAN) remains at 19 digits. The PAN comprises the IIN, the individual account identifier, and the check digit, so when using an eight digit IIN, the maximum length of an individual account identifier would only be 10 digits. Check digit The final digit is a check digit which is calculated using the Luhn algorithm, defined in Annex B of ISO/IEC 7812-1. References American Bankers Association Identifiers 07812