The Withdrawal Agreement between the European Union and the United Kingdom sets out the conditions for an orderly withdrawal of the United Kingdom from the EU in accordance with Article 50 of the Treaty on European Union. The UK has decided to introduce a system that requires EU citizens to apply for a new residency status, known as “sedentary” or “pre-established”. It is still unclear whether each of the 27 EU members will exercise its discretion under the Withdrawal Agreement to require UK residents to apply for new residency status. The UK voted to leave the EU in a referendum on 23 June 2016. On the 29. In March 2017, then-British Prime Minister Theresa May wrote to European Council President Donald Tusk, triggering Article 50 of the Treaty on European Union, launching the process for an EU member state to leave the Union. The procedure provided for in Article 50 provides for a period of two years for the negotiation of a Withdrawal Agreement, which should take into account the future relationship between the EU and the outgoing Member State. Finally, at the request of the United Kingdom, the deadline set out in paragraph 50 was extended until 31 January 2020. On 17 October 2019, the EU and the UK agreed on the text of a withdrawal agreement, which was unanimously approved by the European Council. If no agreement is reached by that date, the UK will leave the single market on 1 January 2021 without a trade agreement. A non-binding political declaration on the future relationship between the EU and the UK is closely linked to the Withdrawal Agreement.