This document is an excerpt from the EUR-Lex website
Article 50 of the Treaty on European Union provides for a mechanism for the voluntary and unilateral withdrawal of a country from the European Union (EU).
An EU country wishing to withdraw must notify the European Council of its intention to do so. The European Council is then required to provide guidelines for the conclusion of an agreement setting out the arrangements for that country's withdrawal.
This agreement is concluded on behalf of the EU by the Council, acting by qualified majority, having obtained the European Parliament's consent.
The EU treaties cease to apply to the country in question from the date of entry into force of the agreement, or within 2 years of the notification of the withdrawal. The Council may decide to extend that period.
Any country that has withdrawn from the EU may apply to rejoin. It would be required to go through the accession procedure.