The Application Identifier (AID) is a value that indicates the program / routine used to process EMV Transaction Data. Both the Terminal and the Card have a list of AIDs that they have been programmed to use in transaction processing. A fully-qualified AID contains both an RID and a PIX. The RID (Registered Application Provider ID) is the first 10 characters of the AID and designates the Payment Scheme (ISO 7816-4). PIX is the Proprietary Application Identifier Extension — the part of the AID after the first 10 characters. Tag 4F stores the AID for the card; Tag 9F06 stores the AID for the Terminal; Tag 84 provides the Dedicated File Name (typically the AID). The Applications that both the Card and the Terminal have in common form the "Candidate List." If the Candidate List is empty, the transaction falls back to Mag Swipe, which means that the transaction will not be processed as an EMV transaction. Following is a list of common Application Identifiers.