MIC & ISO Market Codes

The Market Identifier Code, specified by ISO 10383, is the four-letter code for an exchange or regulated venue: XNYS for the New York Stock Exchange, XLON for London, XNAS for Nasdaq. MICs ride inside FIX tags and MiFID transaction reports, saying where a price was actually seen. The same ISO family supplies ISO 4217 three-letter currency codes such as USD and EUR, and ISO 20022, the messaging standard replacing proprietary payment and settlement formats. Together they explain why a bare ticker is never enough: the MIC says where, the currency code says in what money, and the message standard moves the record safely between systems.