ISO 4217 is a standard published by the International Standards Organization, which delineates currency designators, country codes (alpha and numeric), and references to minor units in three tables:

The tables, history and ongoing discussion is maintained by SIX Interbank Clearing.

The ISO 4217 code list is used in banking and business globally. In many countries the ISO codes for the more common currencies are so well known publicly that exchange rates published in newspapers or posted in banks use only these to delineate the different currencies, instead of translated currency names or ambiguous currency symbols. ISO 4217 codes are used on airline tickets and international train tickets to remove any ambiguity about the price.

The first two letters of the code are the two letters of ISO 3166-1 alpha-2 country codes (which are also used as the basis for national top-level domains on the Internet) and the third is usually the initial of the currency itself. So Japan's currency code is JPY—JP for Japan and Y for yen. This eliminates the problem caused by the names dollar, franc and pound being used in dozens of different countries, each having significantly differing values. Also, if a currency is revalued, the currency code's last letter is changed to distinguish it from the old currency. In some cases, the third letter is the initial for "new" in that country's language, to distinguish it from an older currency that was revalued; the code sometimes outlasts the usage of the term "new" itself (for example, the code for the Mexican peso is MXN). Other changes can be seen, however; the Russian ruble, for example, changed from RUR to RUB, where the B comes from the third letter in the word "ruble".