MPs have tabled a series of amendments to the government's Brexit motion in an attempt to take control of the process.
Seven amendments have been tabled so far, but others can be submitted at the last minute.
It is up the Speaker John Bercow to decide which ones MPs will vote on.
He is unlikely to select two amendments which cover the same issue.
Votes are expected from 10pm tonight.
Labour
The Labour Party's amendment calls for MPs to be given a say on the next steps this week.
These could include Labour’s alternative plan which includes a customs union, close alignment with the single market and alignment on rights and protections.
Other possible options which MPs could have a say on include Common Market 2.0, a customs union and a second referendum.
Liberal Democrats
Seeks a two-year extension to provide time for a referendum on accepting the withdrawal agreement or remaining in the EU.
It has the support of the Independent Group of MPs.
Oliver Letwin
The proposal seeks to pave the way for a series of indicative votes in the Commons on Wednesday, effectively taking control of the Brexit process out of the hands of the Government.
Sir Oliver acknowledged that any votes would be advisory rather than binding on the Government and it may take several rounds of voting before a majority is found for any of the options - if one can be found at all.
The amendment does not specify the form of voting to be used.
He said Mrs May "hasn't been able to get a majority and we don't know what she could get a majority for, so once we find that out there is a way forward, in principle, and then the next thing would be for the Prime Minister to take that forward and for the Government to implement it".
This amendment has cross-party support including from Conservative Dominic Grieve and Labour's Hilary Benn, who is also chair of the Brexit Committee.
Will Quince
The Tory backbencher has put forward an amendment which reaffirms a commitment to honour the result of the referendum.
It emphasises the fact that as well as Leave winning the 2016 referendum, 85% of votes were cast for parties to implement Brexit in 2017.
It has support from DUP Westminster leader Nigel Dodds and members of the European Research Group including Jacob Rees-Mogg.
Yvette Cooper
If a deal is not passed by Thursday, the government has to set out how it will ensure the UK does not leave without a deal on 12 April, "including by seeking an extension to Article 50 to take account of any conclusions reached by the House"
This could be seen as complimentary to the Letwin amendment, as it gives space to reflect on the results of indicative votes
It has support from Conservatives Oliver Letwin, Caroline Spelman and Nick Boles - as well as from Labour MPs and the Independent Group.
The Independent Group
The newly-formed Independent Group have put forward an amendment for a second referendum or People's Vote.
It is not the same as the Lib Dem amendment which calls for a referendum between the prime minister's deal and remain.
Instead TIG amendment calls for preparations for a referendum between leaving the EU on terms decided by parliament and staying in the EU.
But it does have Lib Dem support.
Dame Margaret Beckett - so-called no deal lock
The former Foreign Secretary has put forward an amendment designed to introduce a system to stop the UK from crashing out without a deal.
If the UK is seven days away from leaving without a deal, government must allow MPs to vote on whether to leave without a deal or request an extension "to give time for Parliament to determine a different approach"
