The single currency of the 11 countries that are members of the European Monetary Union, one of the institutions of the European Union. This new currency went into effect on January 1, 1999. The participating countries are Austria, Belgium, Finland, France, Germany, Ireland, Italy, Luxembourg, Netherlands, Spain, and Portugal. The exchange rates for the currencies of these 11 countries were irrevocably fixed in terms of the euro on December 31, 1998. Although the euro is now the official currency, the transition will occur in two phases. For financial transactions, the euro replaced national currencies on January 1, 1999, but for notes and coins, it will replace national currencies in 2002. Four EU members did not join the launch of the euro in January 1999: Denmark, Greece, Sweden, and the United Kingdom.