Ambassadors for the European Union's 27 member states have unanimously approved the provisional application of a post-Brexit trade deal on Jan. 1, a German spokesperson confirmed on Monday.

Why it matters: It's an expected, but crucial step in staving off a potentially catastrophic "no-deal" Brexit on Jan. 1, coming days after the U.K. government and European Commission announced they had reached a stunning breakthrough after months of stalled negotiations.

What to watch: The U.K.'s House of Commons will meet to vote on the deal on Wednesday.

• The leader of the opposition Labour Party, Keir Starmer, has urged lawmakers to back the deal, all but ensuring that Prime Minister Boris Johnson will have the votes he needs for the agreement to sail through Parliament.
• The European Parliament will vote to fully approve the deal in the new year, but it will still take effect on a provisional basis to avoid a cliff-edge Brexit on Jan. 1.

The big picture: Even with the application of the deal, which outlines many of the terms of the U.K.'s new relationship with its closest and largest trading partner, the British government has warned businesses and citizens to prepare for some "bumpy moments" when the Brexit transition period ends on Dec. 31.

Go deeper: U.K. and EU reach historic post-Brexit trade deal