Brexit was not a single event but a long, complex process that unfolded over more than four years. Understanding the sequence of events helps explain why the outcome looked the way it did, and how the UK-EU relationship reached its current form.
This timeline covers every significant milestone from the referendum announcement to the post-Brexit settlement in force today.
The dates below mark the points at which decisions were made, agreements signed, and the legal status of the UK changed. Each stage built on the last and shaped what came next.
Where disputes arose, particularly over the withdrawal agreement and the Northern Ireland question, those moments are included with enough context to explain why they mattered.
2013 to 2016: The Road to the Referendum
The direct path to Brexit began in January 2013, when Prime Minister David Cameron gave a speech at Bloomberg’s London headquarters pledging to renegotiate the UK’s relationship with the EU and put the result to a referendum.
The Conservative Party won the 2015 general election with a majority, making the referendum commitment a formal government obligation. Cameron subsequently negotiated a package of reforms with EU leaders and announced the vote would take place on 23 June 2016.
Campaigning was intense. The official Leave campaign was led by Vote Leave, while the official Remain campaign operated as Britain Stronger in Europe. Both sides spent heavily and the debate dominated British public life for months.
The result on 23 June 2016 was 51.9% in favour of leaving, on a turnout of 72.2%. David Cameron announced his resignation the following morning.
2016 to 2019: Negotiations and Parliamentary Deadlock
Theresa May became Prime Minister in July 2016 and triggered Article 50 of the Treaty on European Union on 29 March 2017, formally beginning the two-year withdrawal process.
Negotiations with the EU were conducted over 18 months. The key areas of dispute were the financial settlement, citizens’ rights, and the arrangements for the Irish border. A withdrawal agreement was concluded between the UK government and the EU in November 2018.
Parliament rejected the withdrawal agreement on three separate occasions, in January, March, and April 2019. The deadlock forced the UK to request an extension to the Article 50 deadline, which was originally set for 29 March 2019 and was extended first to 12 April, then to 31 October.
Theresa May resigned in June 2019. Boris Johnson was elected Conservative Party leader and became Prime Minister in July 2019.
October 2019 to January 2020: A New Deal and Formal Departure
Boris Johnson renegotiated the withdrawal agreement, replacing the proposed backstop arrangement for Northern Ireland with a new protocol placing a regulatory and customs border in the Irish Sea between Great Britain and Northern Ireland.
Parliament approved the revised withdrawal agreement at second reading in October 2019 but rejected the government’s accelerated timetable. A general election was called for December 2019.
The Conservatives won a substantial majority of 80 seats. Parliament then passed the Withdrawal Agreement Act and the UK formally left the European Union on 31 January 2020 at 11pm GMT.
2020: The Transition Period and the Trade and Cooperation Agreement
From 1 February to 31 December 2020, the UK remained inside the EU’s single market and customs union during a transition period. EU law continued to apply and free movement remained in place.
Negotiations on the future UK-EU trade relationship took place throughout 2020. The talks were extended repeatedly as agreement proved difficult to reach on fisheries, the level playing field provisions, and governance arrangements.
The Trade and Cooperation Agreement was agreed on 24 December 2020, just days before the transition period expired. It was provisionally applied from 1 January 2021 and formally ratified by both sides in April 2021. Free movement ended, new customs and regulatory requirements came into force, and the UK fully operated outside EU structures for the first time in 47 years.
2021 to Present: Life After Brexit
The years since formal departure have involved both implementation of the new arrangements and ongoing negotiation to resolve remaining disputes.
The Northern Ireland Protocol generated significant political tension, with unionists and the UK government arguing it created an unacceptable trade barrier within the UK. Extended negotiations produced the Windsor Framework in February 2023, which modified the original protocol and established new arrangements for the movement of goods between Great Britain and Northern Ireland.
The UK has since signed trade agreements with Australia, New Zealand, and agreed in principle to join the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP). Negotiations with the United States have been more complex and a deal remains outstanding as of the time of writing.
The UK-EU relationship continues to be managed through bodies established under the Trade and Cooperation Agreement. Both sides have undertaken reviews and adjustments, and further developments in areas such as youth mobility, data adequacy, and security cooperation remain under discussion.