An accession country that plans to join the Union must align many aspects of its society – social, economic and political – with those of EU Member States. Much of this alignment is aimed at ensuring that an accession country can operate successfully within the Union’s single market for goods, services, capital and labour – accession is a process of integration.

Adopting the euro and joining the euro area takes integration a step further – it is a process of much closer economic integration with the other euro-area Member States. Adopting the euro also demands extensive preparations; in particular it requires economic and legal convergence.

Why are there conditions for entry to the euro area?

Adopting the single currency is a crucial step in a Member State's economy. Its exchange rate is irrevocably fixed and monetary policy is transferred to the hands of the European Central Bank, which conducts it independently for the entire euro area. The economic entry conditions are designed to ensure that a Member State's economy is sufficiently prepared for adoption of the single currency and can integrate smoothly into the monetary regime of the euro area without risk of disruption for the Member State or the euro area as a whole. In short, the economic entry criteria are intended to ensure economic convergence – they are known as the 'convergence criteria' (or 'Maastricht criteria') and were agreed by the EU Member States in 1991 as part of the preparations for introduction of the euro.

In addition to meeting the economic convergence criteria, a euro-area candidate country must make changes to national laws and rules, notably governing its national central bank and other monetary issues, in order to make them compatible with the Treaty. In particular, national central banks must be independent, such that the monetary policy decided by the European Central Bank is also independent.

National target dates for adoption of the euro

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. Seven of the 13 Member States who joined the EU since 2004 have already joined the euro area, most recently Lithuania on 1 January 2015.