An acquirer identification number is a code that identifies the acquiring institution in a card transaction. Card networks assign acquirers identifiers when they become members, and those identifiers travel in authorisation messages and clearing files so that responses, settlement amounts and later disputes reach the right acquiring bank. In the ISO 8583 message standard used for card payments, a data field carries the acquiring institution identification code, and in practice acquirers often use a BIN-style range for this purpose, sometimes called an acquirer BIN. Networks use their own terms: Mastercard, for example, refers to member identifiers known as ICA numbers. The acquirer identifier differs from the merchant identification number, which identifies a single merchant at that acquirer, and from the issuer's BIN. Also see payment acquirer.