The transaction currency for security trades is usually established by each market separately. Generally there is only one specific transaction currency for a certain type of security. One can actually start buying these securities with any type of currency, other than the one specified; however the amount will be automatically converted to fit the requirements of the respective currency. (USD – stands for U.S. dollar, CAD for the Canadian dollar, EUR for the European Euro for example). So, if the trade sells only in USD, but the investor wishes to enter the transaction and pay with EUR, the amount in EUR will be exchanged into USD so that the transaction can take place.