A CFI code (Classification of Financial Instruments code) is an ISO standard code that classifies a security. CFI codes consist of six letters. The first letter indicates the type of instrument, the second a finer sub-classification, and the remaining letters show various attributes of the security.
For example, the CFI code ESVUFA indicates:
So a security described by this code is a fully paid ordinary share that is registered: the type of shares most commonly traded on stock exchanges.
CFI codes are a descriptions of types of securities. They do not identify financial instruments. They serve a very different purpose from ISIN similar codes which uniquely identify particular instruments.
CFI codes provide a standardised description of the characteristics of securities so that automated systems can handle clearing, settlement and other processing appropriately.