The euro is the most tangible proof of European integration: around 341 million people use it every day, making it the second most-used currency worldwide. The benefits of the common currency are immediately obvious to anyone travelling abroad or shopping online on websites based in another EU country.
Currently, the euro (€) is the official currency of 19 out of 28 EU member countries.
Although all EU countries are part of the Economic and Monetary Union (EMU), 19 of them have replaced their national currencies with the single currency – the euro. These EU countries form the euro area, also known as the eurozone.
These are countries where the euro has still not been adopted, but who will join once they have met the necessary conditions. Mostly, it consists of countries of member states which acceded to the Union in 2004, 2007 and 2013, after the euro was launched in 2002.
Occasionally, member states can negotiate an opt-out from any of the European Union legislation or treaties, and agree to not participate in certain policy areas. Concerning the single currency, this is the case for the United Kingdom and Denmark. Both these countries kept their currency after becoming members of the EU.
In order to join the euro area, EU member states are required to fulfil so-called 'convergence criteria'.
These binding economic and legal conditions were agreed in the Maastricht Treaty in 1992 and are also known as 'Maastricht criteria'. All EU Member States, except Denmark and the United Kingdom, are required to adopt the euro and join the euro area, once they are ready to fulfil them.
The Treaty does not specify a particular timetable for joining the euro area, but leaves it to member states to develop their own strategies for meeting the condition for euro adoption.
The European Commission and the European Central Bank jointly decide whether the conditions are met for euro area candidate countries to adopt the euro. After assessing the progress made against the convergence criteria, the two bodies publish their conclusions in respective reports. These are further ratified by the ECOFIN Council in consultation with the Parliament and Heads of State. If favourable, the adoption process can begin.