A government spokesman made the announcement Monday, saying the EU has been informed of the development.
Article 50 of the EU's treaty covers how a member can withdraw.
The breakup began with a June 2016 referendum in which British voters narrowly chose to leave the EU. The vote appeared to be driven by anti-establishment sentiments and the feeling the EU governing structure has taken too much control away from the common British citizen.
The referendum also brought the resignation of former Prime Minister David Cameron, who during a re-election campaign had promised to hold the vote.