Brexit vote on Christmas? Dash to ratify any agreement

After their negotiating teams strike a deal, both sides will begin a race to approve the accord formally before the post-Brexit transition period expires at 11 pm London time on Dec. 31.

The UK and the European Union will have only days to ratify any post-Brexit trade agreement -- if they manage to reach one this week.

European Union (EU) flags outside the Berlaymont building near a mural reading 'The Future Is Europe' in Brussels, Belgium. (Bloomberg)

After their negotiating teams strike a deal, both sides will begin a race to approve the accord formally before the post-Brexit transition period expires at 11 pm London time on Dec. 31.

In Britain, Prime Minister Boris Johnson has promised lawmakers a vote, and hasn’t ruled out holding one on Christmas Day. In Brussels, the process is more complex, involving the bloc’s 27 national governments as well as the European Parliament.

There’s a remote chance the process could be delayed by a last-minute intervention by an EU leader like French President Emmanuel Macron, or by opposition in the European or British parliaments. If a deal isn’t approved in time, it could be applied provisionally, pending parliamentary approval -- or Britain could be left facing a spell outside the EU without a trade deal.