BREXIT: WHAT HAPPENS NOW ?

Source: Peter BarnesSenior elections and political analyst, BBC News

No-deal Brexit on 31 October

The default position is the UK will leave the EU on 31 October at 23:00 GMT. Prime Minister Boris Johnson says he wants a new deal with the EU on the terms of leaving, but has vowed Brexit will happen on 31 October even if that is with no deal. Leaving without a deal (or withdrawal agreement) means the UK would immediately exit the customs union and single market - arrangements designed to make trade easier. Many politicians and businesses say this would damage the economy. Others say the risks are exaggerated.

MPs try to pass a new law to stop no deal

MPs have voted more than once to show they oppose a no-deal Brexit, and opposition parties and some Conservative backbenchers will now try to push through legislation to stop it happening. But the decision to suspend Parliament - known as prorogation - as early as Monday, 9 September, means they have very little time. They have already taken control of the parliamentary schedule. Now they will try to pass a new law - to try to make the government ask the EU to delay Brexit until 31 January 2020. This law will be debated and voted on in the House of Commons on Wednesday 4 September, and could move to the House of Lords on Thursday 5 September. If passed, the bill could be given royal assent by the Queen and become law on Monday 9 September.

Snap election

Prime Minister Boris Johnson is seeking to hold an early election. He wants this to be on 15 October. He needs two-thirds of MPs to support an early election. Theoretically, there is another way he could achieve his goal. A short new law specifying the date of an early general election would require only a simple majority and not need two-thirds of MPs. If polling day was set before 31 October, then what would happen next on Brexit would depend on the outcome of the election.

Vote of no confidence

If the effort to pass legislation stopping a no-deal Brexit fails, it would be possible to table a vote of no confidence in the government. Labour leader Jeremy Corbyn has previously said he would do this. And if more MPs vote for the no-confidence motion than against it, there would then be a 14-day window to see if the current government - or an alternative one with a new prime minister - could win a vote of confidence. A new government appointed in this way would probably then seek a Brexit delay - perhaps to hold a general election or another referendum. But if no-one wins a confidence vote, triggering a general election Mr Johnson goes into as prime minister, he could choose to hold it after 31 October, when Brexit would have already happened.

Pass a deal by 31 October

The government's preferred option to prevent a no-deal Brexit is for the UK Parliament to ratify a withdrawal agreement with the EU before the end of October. But the existing deal negotiated by Theresa May and her government has been defeated in the House of Commons several times - and Boris Johnson has said it is dead. The government hopes it can secure a new deal from the EU - or an amended version of the existing deal without the Irish backstop, which the government opposes. The backstop is a measure aimed at preventing any possibility of border posts and checks between Northern Ireland and the Republic of Ireland. But while the EU has said it would consider any new UK proposals, it has repeatedly stated the backstop is a critical part of the deal.

Delay Brexit

Even if those opposing a no-deal Brexit succeeded in making the government seek a delay, the UK can't unilaterally decide to delay Brexit - that would have to be agreed unanimously by the other EU member states. However, it has previously been possible to agree extensions and the other states might be persuaded, if they thought the alternative would be a no-deal Brexit.

Cancel Brexit

There is also the legal option of cancelling Brexit altogether by revoking Article 50. But clearly, this is not something the current government is contemplating - so it's only really possible to imagine this outcome after a change of government.