FACTBOX-Britain's big Brexit vote: What happens in parliament?
To try to get that approval, May and her ministers will spend five days debating the issue in parliament, where they will have to overcome opposition from across the political spectrum, and defeat attempts to alter or delay her Brexit process or derail it altogether.
Here's how the voting will work:
The debate is taking place in the lower house of parliament, the House of Commons. May does not have an outright majority of the 650 lawmakers, and the DUP, the small Northern Irish party that usually props up her government, is opposed to the deal.
The debate is scheduled for Dec. 4, 5, 6, 10 and 11. Each day's debate will last up to eight hours, with start and finish times likely to vary.
On the final day, there will be a series of votes: first, to approve or reject up to six amendments to the government's motion, and then to approve or reject the motion. Voting is due to start at 7 p.m. (1900 GMT).
The debate will be on whether to approve a motion stating that parliament has approved the Withdrawal Agreement - a legal text setting out the terms of departure - and a separate political declaration outlining the long-term relationship Britain will have with the EU.
WHAT ARE AMENDMENTS?
Lawmakers are able to put forward amendments to this motion. John Bercow, the Speaker of the House, chooses no more than six of these on the final day, and they will be voted on unless the proposers opt to withdraw them.
By Tuesday, six amendments had been submitted for Bercow to consider.
If approved, an amendment would be included in the wording of the final motion. While any successful amendments would not bind the government to comply with them, they would be politically hard to ignore, and could dictate May's next steps.
Ministers have expressed concerns that if any amendment is passed by parliament, it could prevent the deal being ratified because the final vote may not then provide the legally necessary clear and unequivocal approval of May's deal.
The amendments will be voted on before the deciding ballot on whether to approve the overall motion - meaning May has to win a series of votes, rather than just one, each with the potential to scupper her plan.
WHAT ARE THE AMENDMENTS?
The opposition Labour Party has submitted an amendment designed to ensure that the government cannot leave the EU without an exit agreement and must consider all alternatives to doing so.
A cross-party group of lawmakers have also submitted a similar amendment, blocking May's deal and ruling out a "no-deal" Brexit, and then giving parliament a greater say over what happens next.
Several lawmakers have submitted separate amendments requiring the government to rethink the arrangements around the so-called 'backstop' on Northern Ireland, designed to prevent the installation of border infrastructure on the land frontier with Ireland - a so-called "hard border". One demands that the government instead seek a trade deal with the EU modelled on the deal that the EU has with Canada.
HOW WILL THE RESULT BE ANNOUNCED?
Once the debate is finished, the speaker will typically ask those in favour of each amendment to shout "aye", and then those against to say "no". As long as some lawmakers shout "no", the speaker will call a formal vote, known as a division.
Votes are registered by lawmakers walking through different doorways, out of sight of television cameras and onlookers. Once the headcount is complete - which can take up to 15 minutes - lawmakers return to the debating chamber.
Four appointed tellers will assemble in front of the speaker, and one will read the result out loud.
Once all the amendments have been voted upon, the main motion is put to a vote using the same process.
WHAT HAPPENS IF SHE LOSES?
By law, if the deal is rejected, ministers have 21 days to state how they intend to proceed. The government has previously said that if the agreement is rejected, Britain will leave the EU without a deal.
The reality is that the huge uncertainty in the world's fifth largest economy and the likely adverse reaction of financial markets would demand a much quicker political reaction.
For more on possible next steps, see:
(Reporting by William James; Editing by Kevin Liffey/Guy Faulconbridge)
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)