The US Dollar, which is the official currency of The United States, has the ISO 4217 Code of USD. The corresponding ISO-4217 Code Number for USD is 840. The USD ISO code has a currency exponent of 2.

The International Organization for Standardization (ISO) is an international standard setting body of representatives from several national standards organizations.

ISO 4217 is the international standard describing three-letter codes known as the currency code. (Example:USD is the currency code for the The United States US Dollar) This code defines the names of currencies established by the International Organization for Standardization (ISO). ISO 4217 are the accepted codes used by banking institutions, businesses, and individuals worldwide for defining different currencies. Using these codes helps to eliminate any confusion regarding currency names and symbols that can occur during translation.

The first two letters of the ISO 4217 code are the two letters of ISO 3166-1 alpha-2 country codes. These are the same two letters that are also used as the basis for national top-level domains, such as .de, .us, .fr, etc.. The third letter is usually the initial of the currency itself. For example, Japan's currency code is JPY, JP for Japan and Y for yen. This eliminates the problems caused by the names dollar, franc and pound being used in several different countries. If a currency is revalued, the currency code's last letter is changed to distinguish it from older currency. Sometimes, the third letter is the initial for "new" in that country's language. For example, the Mexican peso is MXN, the N is for "nuevo", the Spanish word for "new". However this method is not always the rule. For example, the Russian ruble was changed from RUR to RUB, because it was decided to use a "B" the third letter in the word "ruble".

A three digit code number is also assigned to each currency. This numeric code is usually the same as the ISO 3166-1 numeric code. For example, the USD (United States dollar) has the code 840.

For more information on ISO 4217 please refer to The International Organization for Standardization located at http://www.iso.org/iso/home.html