The Treaty of Maastricht instituted the euro as the currency of the Economic and Monetary
Union (Article 3.4 Treaty on European Union), the single monetary policy for participating
countries (the eurozone) and the eurozone monetary authority – comprising the National
Central Banks (NCBs) of the European Union and, at its centre, the European Central Bank
(ECB), together constituting the European System of Central Banks (ESCB). The Eurosystem
is made up of the ECB and the (currently 19) NCBs whose currency is the euro. The ECB
coordinates operations and the NCBs execute the transactions, such as providing funds to
banks, settling cross-border transactions and managing foreign exchange reserves. The ECB
must be consulted, and may submit opinions, on any matter in its field of competence
(Article 127.4 Treaty on the Functioning of the European Union, TFEU).