On 23 June 2016, the UK made a referendum that asked whether the UK should leave the EU. The result was that 51.9% of the UK electorate (the main region of the UK) voted that the UK should leave the EU. The rest wanted the UK to stay in the EU. On 29 March 2017, the UK government said that they will definitely be leaving the EU. This started the procedure of Article 50 of the Treaty on European Union, a law that deals with countries that leave the EU. The UK was expected to fully leave the EU on 29 March 2019 at 11 p.m. UTC. The deadline to leave was later changed to 31 October 2019.
Below is a timeline of major events relating to Brexit.
- 23 June: The UK holds a referendum on whether to leave the European Union. 51.9% of voters vote to leave.
- 24 June: David Cameron announces that he will resign as Prime Minister. He is replaced by Theresa May.
- 13 July: Theresa May accepts the Queen's invitation to form a government. David Davis joins the Secretary of State for Exiting the European Union to monitor any withdrawal negotiations.
- 27 July: The European Commission selects French politician Michel Barnier to be the European Chief Negotiator for the United Kingdom Exiting the European Union. Michel Barnier will provide support in engaging negotiations with the United Kingdom and the EU.
- 7 December: Article 50 is favored by a vote of 461 to 89 by the UK House of Commons. It would be planned to be added by the end of March 2017.
- 24 January: The Parliament must pass legislation (approve of this rule) before Article 50 can be accepted as a law. The UK Supreme Court says that the Parliament must follow this new rule, as explained by the Miller case.
- 26 January: The UK Government introduces a 137-word bill in Parliament. This ensures that Theresa May can enforce Article 50. Labour leader Jeremy Corbyn instructs his MPs to support it.
- 16 March: The bill receives Royal Assent (royal approval).
- 29 March: A letter from Theresa May is handed to President of the European Council Donald Tusk to convince him to approve Article 50. Starting from 29 March 2017, the UK will begin to leave the EU by 29 March 2019, a two-year process.
- 8 April: Theresa May announces that a general election will take place on 8 June.
- 8 June: A general election is held in the UK. The Conservative Party remains the largest single party but loses its majority. They form a minority government with a confidence-and-supply arrangement with the Democratic Unionist Party (DUP) of Northern Ireland.
- 19 June: Brexit negotiations begin.
- 25 November: All EU members accept a withdrawal agreement.
- 15 January: The UK House of Commons reject the agreement.
- 21 March: The UK House of Commons reject it again. Instead, they decided to extend the due date to 31 October instead of 29 March.
- 24 July: Boris Johnson becomes the prime minister of the United Kingdom.
- 19 October: The UK House of commons rejects Boris' deal and force the prime minster to write to the EU asking to extend the due date to 31 January 2020 instead of 31 October 2019.
- 28 October: The European Council agrees to extend the Brexit deadline until 31 January 2020.
- 6 November: Parliament is dissolved as a general election is announced to take place on 12 December.
- 12 December: A general election is held in the UK. The pro-Brexit Conservative party remains the largest party and gains a majority of 80 seats. Labour suffers their worst election since 1935.
- 20 December: The withdrawal agreement is passed meaning the UK will leave the EU on 31 January.
- 31 January: The UK membership with the EU comes to an end. The UK will now enter the transition period for 11 months. This means that the UK will still be guaranteed customs union and single market (free trade) until 31 December.
- 1 July: The deadline for the UK to extend the transition period.
- 31 December: The date the UK is set to leave the EU. The transition period was not extended. 
- "Brexit preparedness". European Commission. Retrieved 24 April 2018.
- Tusk, Donald (10 April 2019). "EU27/UK have agreed a flexible extension until 31 October. This means additional six months for the UK to find the best possible solution". @eucopresident. Twitter. Retrieved 11 April 2019.
- See also Khetani-Shah, Sanya; Deutsch, Jillian. "Brexit timeline: From referendum to EU exit". Politico Pro. Retrieved 9 October 2019.
- MPs vote to demand Brexit plan and say article 50 should be triggered by the end March – as it happened (Guardian). Retrieved 29 March 2019.