Interbank National Authorization System (INAS)

See: Interbank. See: Interbank Network for Electronic Transfer - INET.

MasterCard is one of the big credit card companies. It uses a network of banks to facilitate its transactions, a group of finance partners connected by a sophisticated telecommunications network that allows you to use your MasterCard to buy something in Istanbul and have the transaction get processed nearly instantly, even though the card is issued out of St. Louis.

The Interbank National Authorization System, or INAS, is the version of this network that was used by MasterCard International. There was a separate U.S. version called Interbank Network for Electronic Transfer, or INET, used by MasterCard.

The two networks (INAS and INET) have been combined into a single network called Banknet.