Article 50 of the Treaty on European Union establishes the procedures for a member state to withdraw from the EU. It requires the member state to notify the EU of its withdrawal and obliges the EU to then try to negotiate a withdrawal agreement with that state.
Britain's "Leave" vote, however, does not represent that formal notification. That notification could take place within days — for example, when EU member countries meet for a summit that is scheduled for June 28 to 29. Or British officials might wait a few months to pull the trigger.
Once Britain invokes Article 50, it will have a two-year window in which to negotiate a new treaty to replace the terms of EU membership. Britain and EU leaders would have to hash out issues like trade tariffs, migration, and the regulation of everything from cars to agriculture.
In the best-case scenario, Britain may be able to negotiate access to the European market that isn’t that different from what it has now. Norway is not a member of the EU, but it has agreed to abide by a number of EU rules in exchange for favorable access to the European Common Market.