What does Issuer Identification number (IIA) mean?

Formerly known as BIN (Bank Identification Number), the Issuer Identification Number is basically the first six numbers you can see on a credit card, because this number series gives an identification of the issuing institution (bank). For example, American express’s IIN starts 37, and then has additional digits for each type: American Express Platinum 3713, Blue Cash American Express Card has 3723 95 while Blue American Express Card has 3746 71; the Visa’s IIN starts with 40 and again has additional different digits for each Visa card type.

Identifying the issuer in the first place is an important step, because it might happen that the acquirer observes that the IIN on the card corresponds to some internationally based banking institution, so then further details are needed in order to clear the transaction.