A reader trying to place the Brexit timeline in order can anchor it on the referendum on 23 June 2016, Article 50 on 29 March 2017, departure on 31 January 2020 and the transition end on 31 December 2020.
Dates are easy to mix up because the planned leaving date moved several times, and leaving was not the same event as the end of transition. In short, the UK left the EU on 31 January 2020, and the transition period ended on 31 December 2020, as Kennedys Law’s timeline records. Each entry below states what changed on its date, in order.
For what these dates meant for residents and their status, the guide to eu citizens rights after brexit picks up where this chronology stops.
23 June 2016: the EU referendum
The 2016 EU referendum took place on 23 June 2016. According to Al Jazeera’s timeline, leave won with 51.9% of the vote against 48.1% for remain. This is the entry to use for any question about the public vote and its result.
It suits readers who need the starting point of the story, and it has one clear limit. The vote set the political direction but did not itself take the UK out of the EU. Leaving needed a formal legal step, which came with the notification in the next entry, and so the referendum date should never be quoted as the date the UK left.
29 March 2017: Article 50 is triggered
The UK formally notified the European Council of its decision to withdraw from the EU on 29 March 2017, according to Kennedys Law. That notification triggered a two-year timeframe to negotiate a withdrawal agreement. Al Jazeera lists the same date as the day Article 50 was triggered.
This is the entry that turns a referendum result into a legal process. The two-year timeframe explains why 29 March 2019 appears in the same Al Jazeera timeline as the planned Brexit day, the day the UK was due to leave and enter a transitional period. Anyone asking when withdrawal formally began should use 29 March 2017, not the referendum date. Readers who want the clause itself, rather than its date, can follow the explainer on what is Article 50.
November 2018 to January 2019: the Withdrawal Agreement and the Commons vote
The Withdrawal Agreement was published on 14 November 2018, and the leaders of EU countries officially endorsed it on 25 November 2018, according to Al Jazeera. The same timeline records that MPs in the House of Commons voted by 432 to 202 on 15 January 2019 to reject the deal.
This entry is the pivot of the whole chronology. It suits readers who want to understand why 2019 was crowded with deadlines. The vote did not end the Brexit process, and it is not a leaving date. It is the reason the next entry exists.
March to October 2019: the extensions
The original Brexit day was 29 March 2019, the day Al Jazeera lists as the date the UK would officially leave the EU. It did not leave then. Instead the Article 50 deadline was moved by agreement between the UK and the EU27, the remaining member states, with the European Council as the forum where leaders decided.
The sequence followed the Commons rejection of the deal. The Prime Minister wrote to the European Council asking for more time, and the EU leaders answered with shorter or longer extensions. The table sets out the dates, which is the clearest way to see why deadlines were extended: each new date was a negotiated pause, not a departure.
| Date | What happened | Deadline named | Planning use |
|---|---|---|---|
| 20 March 2019 | Prime Minister writes to the European Council asking to extend Article 50 | 30 June 2019 (requested) | Treat as a request, not an agreed date |
| 21 March 2019 | EU27 leaders grant a short extension | 12 April or 22 May | Cite both dates, because the grant named alternatives |
| 10 April 2019 | UK and EU27 agree to extend Article 50 | 31 October 2019 | The longer extension that replaced the earlier alternatives |
| 28 October 2019 | EU agrees to a further Brexit extension | 31 January 2020 | The deadline the UK actually met |
The dates in the table are taken from Kennedys Law’s Brexit timeline.
The practical lesson is to keep requested, granted and met dates apart. Of the dates in the table, only 31 January 2020 became the day the UK left, so 12 April, 22 May, 30 June and 31 October should be described as deadlines that passed, not as Brexit days.
31 January 2020: the UK leaves the EU
The European Union (Withdrawal Agreement) Bill became law on 23 January 2020, and the UK left the EU on 31 January 2020, according to Kennedys Law. That is the answer to when the UK formally left. The leaving date was the one agreed on 28 October 2019, so it closed the extension sequence.
Parliament had rejected the first version of the deal in January 2019, and the withdrawal legislation only became law in January 2020. This entry suits readers who need the date of formal departure. It does not suit readers asking when new trading arrangements applied, because the same Kennedys timeline shows the transition period was due to end on 31 December 2020.
31 December 2020: the transition period ends
The transition period ended on 31 December 2020, as both Kennedys Law and Al Jazeera record. On 1 January 2021 the new UK-EU relationship began and the Northern Ireland Protocol came into effect, according to Kennedys.
This is the date to use for the end of the transition, and it is separate from the leaving date. Leaving ended membership. The end of transition is when the new relationship started, which is why it is the entry that matters most to businesses and travellers rather than to constitutional history. Questions about how EU-derived legislation was handled at home belong to a different guide, which explains what is retained EU law.
Choosing the right date for your purpose
Which entry to quote depends on the question being answered. The dates come from Kennedys Law and Al Jazeera, and this short checklist maps each purpose to one date.
- Public vote or result: use 23 June 2016 and the 51.9% to 48.1% split.
- Start of formal withdrawal: use 29 March 2017, when the UK notified the European Council.
- Why 2019 saw repeated deadlines: use 15 January 2019 for the Commons vote, then the extension table.
- Formal departure: use 31 January 2020, not an earlier deadline.
- End of transition and the start of the new relationship: use 31 December 2020 for the end and 1 January 2021 for the new arrangements.
Frequently asked questions
Could the UK have cancelled Article 50?
The Court of Justice ruled on 11 December 2018 that the UK could unilaterally revoke Article 50, according to Kennedys Law.
Who announced the referendum date?
David Cameron announced the date on 22 February 2016, setting the vote for 23 June 2016, according to Al Jazeera.
When did Parliament vote to rule out a no-deal Brexit?
Parliament voted to rule out a no-deal Brexit on 13 March 2019, per Kennedys Law.
When did the EU Parliament ratify the Trade and Cooperation Agreement?
Kennedys Law’s timeline lists the EU Parliament’s ratification of the Brexit trade deal, the Trade and Cooperation Agreement, on 28 April 2021.