Update: Theresa May's withdrawal agreement has been defeated for the third time in the House of Commons today.
British MPs rejected her deal by 286 votes to 344, a majority 58.
Mrs May said: "I fear we are reaching the limits of the process in this House.
“The legal default now is that the United Kingdom is due to leave the European Union on April 12 – in just 14 days’ time. This is not enough time to agree, legislate for and ratify a deal, and yet the House has been clear it will not permit leaving without a deal.
“And so we will have to agree an alternative way forward.”
So what are the possible options?
Following the vote, the President of the European Council Donald Tusk announced that he had called a Council meeting for April 10.
That is just two days before the Brexit day of April 12 when a crash out from the EU is possible unless further negotiations or extensions are agreed upon.
The UK has until then to indicate a way forward for consideration by the European Council and must declare whether it will be putting candidates forward to the European elections in May.
The European Commission said this afternoon that a no-deal Brexit was looking like a "likely scenario" on April 12.
"No-deal” scenario on 12 April is now a likely scenario. The EU has been preparing for this since 12/2017. Now fully prepared. We will remain united. Benefits of WA, including transition period, will not be replicated in “no-deal” scenario. Sectoral mini-deals are not an option. pic.twitter.com/JJndIjMtTy— European Commission 🇪🇺 (@EU_Commission) March 29, 2019
MPs voted to oppose a no-deal Brexit, while the British PM has ruled out contesting the elections.
Therefore, the option of a possible extension is likely to be discussed on April 10. However, any further extension beyond April 12 would have to be agreed upon unanimously by the EU.
Further indicative votes are due to take place in Parliament on Monday, with the softer option of a permanent customs union likely to be a prominent issue of debate.
Tory MP Nick Boles put forward a Common Market 2.0 motion for Monday following Mrs May's defeat today.
Another option is to extend Article 50 and hold put Brexit to a people's vote in a second referendum.
Labour leader Jeremy Corbyn said that Mrs May should change her deal or call a general election.
An election has been suggested as a way of breaking the Brexit impasse in Parliament.
British Prime Minister Theresa May is bringing part of her withdrawal agreement to the Commons today as she attempts to convince MPs to vote for her deal.
She will ask politicians to vote on half of the deal which covers the divorce settlement from the European Union.
Given that the future relationship between the UK and the EU, the political declaration, will not be on the table today, it therefore does not constitute a "meaningful vote".
However, it will attempt to meet the condition set down by Speaker John Bercow that Mrs May's deal be sufficiently changed in order to be put to a vote for the third time.
If her deal passes, Brexit will be delayed until May 22.
However, it looks unlikely that the British PM will score a win in Parliament today on what was supposed to be the official leave date.
If the withdrawal agreement is rejected, the UK looks set to crash out of the EU on April 12.
Here are the possible next stages:
Mrs May's withdrawal agreement will be voted on in part in the Commons today and will leave out the political declaration on Britain's future relationship with the EU.
Around 30 Eurosceptics are against the deal, as are the DUP. Party leader Arlene Foster wrote in a Belfast Telegraph opinion piece today that the DUP could not support a "bad deal" which could "undermine the Union".
Theresa May will need support from Labour and independent MPs, however, Jeremy Corbyn said the party could not vote for a “blindfold Brexit”.
In the unlikely event that her deal is passed today, Brexit would be delayed until May 22.
The withdrawal agreement is the draft treaty. After May 22, the UK will enter a transition period for 21 months or more during which talks on a future relationship will take place.
If May's deal passes, she will also be obliged to step down as Prime Minister.
If Mrs May's deal is rejected for a third time, April 12 will be Brexit day.
However, the EU said it "expects the United Kingdom to indicate a way forward before this date for consideration by the European council".
Any further extension beyond April 12 would have to be agreed upon unanimously by the EU.
More indicative votes are set to take place in Parliament on Monday.
In the absence of further extensions or agreement by MPs, a no-deal exit from the EU has the potential to take place on April 12.
During next week's indicative voting session, MPs are likely to vote again on the option of Britain being in a customs union.
The option lost by only eight votes this week, and was one of the most popular proposals put to MPs alongside the vote for a second referendum.
If a permanent customs union is agreed on, the future relationship between the UK and EU could be revised shortly after, with negotiations between the two to take place on the issue.
Under this option, it is still within the realms of possibility that all could be agreed upon by the May 22 deadline.
The British PM has pledged to step down if her deal passes.
Additionally, if MPs vote for a permanent customs union on Monday, Mrs May will be unlikely to support such an option, and if she did, she would split the Cabinet and her party.
A customs union would mean the UK could not create trade deals with non-EU nations, which would be a major sticking point for many in the Conservative party and those in favour of Brexit.
In the event of her resignation, there are up to 10 Cabinet ministers vying for her job, including Boris Johnson who said today that he would support Mrs May's withdrawal agreement.
Other frontrunners include Michael Gove, Jeremy Hunt, Sajid Javid and Amber Rudd.
A general election this year would be the third in four years. It could be a way to break the impasse, but under law, two-thirds of all MPs would need to vote in favour of holding another poll.
The indicative vote on Wednesday championing a second Brexit referendum, the 'confirmatory public vote', lost by a majority of 27.
However, such a process would not be able to take place immediately.
Under UK law, a new piece of legislation would need to be drafted to facilitate the referendum and determine voting rules.
The Electoral Commission would then have to decide what question would be put to the people, which would be then defined in the legislation.
The legislation would have to pass, and a statutory "referendum period" would have to take place.
All of this process could take around 22 weeks, according to the BBC.