Theresa may will have to turn to the EU with an official letter, but when she does, Downing street did not specify.
14 March the house of lords has adopted in its original form the bill giving the government the right to start the exit process. The document allows (although does not formally require) to the Prime Minister to notify the EU about the intention of the United Kingdom to withdraw from the EU, for which voted the majority of British voters in a referendum in June last year.
Signed in 2007 Treaty on European Union, better known as the Lisbon Treaty. It replaced the EU Constitution, which in that year in a referendum rejected by the voters of the two countries-EU members — France and the Netherlands.
The Treaty of Lisbon became the first of the fundamental documents of the EU, which allowed the possibility of withdrawing from the EU member countries. This and devoted article 50 of the document.
Specifically, paragraph 2 of this article, referenced in the bill States that a country wishing to withdraw from the EU adopts the decision in accordance with its Constitution, then the government takes official notice to the governing bodies of the European Union. Shortly after the British referendum on the European Union has specified that this notice may be filed both in writing and verbally — to be entered in the minutes of the meeting of the EU Council, which represents heads of States and governments of all the countries of the Union.
In paragraph 3 of the same article, however, States that the country's membership in the EU shall terminate upon the entry into force of the agreement on the conditions of its release or within two years after the notification, if appropriate agreement could not be reached. However, the Contracting parties may mutually agree to extend the deadline to negotiate the terms of exit.
And experts, and the authors of the article 50 recognized that it is not expected that this provision will ever need to use in practice, and because the order of exit from the EU it is written very vague.