The next key Brexit debate in the House of Commons is scheduled for Tuesday. We look at what MPs will be voting on and what the possible outcomes are.

What is happening on Tuesday and why is it so important?

Early in the Brexit process, MPs insisted that they must have a “meaningful vote” after Theresa May finally struck a deal with the EU. It would not be enough simply to face a choice of between saying yes or no, they said; they wanted to ensure they could vote on amendments proposing an alternative. On Tuesday, as a result of the historic defeat of May’s deal in the Commons earlier this month and procedural moves masterminded by the Tories Viscount Hailsham and Dominic Grieve, MPs will get this chance.

What are the amendments that have been tabled?

There are 19 on the order paper, including amendments to amendments, but more could be submitted. They fall into four categories:

Opposition party amendments. Labour and Liberal Democrats amendments are already down, and one from the Scottish National party is coming on Monday.

Amendments to prevent a no-deal Brexit. The two most important are probably Yvette Cooper’s, enabling the Commons to pass a bill requiring May to seek an article 50 extension if she cannot get her deal passed, and a softer, non-binding one from Caroline Spelman and Jack Dromey, rejecting no deal in principle.

Indicative vote amendments. These are focused on ensuring MPs get more chances to express their views. Hilary Benn has one explicitly demanding indicative votes on Brexit options and Grieve has one saying six days in February and March should be set aside for debates on motions not chosen by the government.

Anti-backstop amendments. The two main ones are from the Tories Andrew Murrison and Graham Brady, calling for the backstop to expire by December 2021 or for it to be removed from the withdrawal agreement altogether.

Why are some of these amendments so controversial?

At least three of the amendments are constitutionally innovative, because they would significantly empower parliament in relation to the executive in the weeks ahead. Mostly the government controls the business in the Commons – ie what gets debated – which means it decides what gets to become law. But the Cooper amendment would create time for a bill that the government would never table itself to be passed in February. And the Grieve amendment, along with a broadly similar Lib Dem one, would enable backbenchers to seize control of Commons business to debate Brexit on particular days before 29 March.

What will happen on Tuesday?

No one can be sure. We do not yet know if the government is tabling its own amendment or whether it will encourage its MPs to back the Murrison/Brady anti-backstop amendments. And we do not know yet which amendments John Bercow, the Speaker, will put to the vote. He has wide discretion and he can call as many has he likes. The order matters, too, because some amendments can in effect knock out others. But he is likely to call a handful. Voting starts at 7pm and if there are, say, six votes, it will finish at about 8.30pm.