Now that's expected to last until the end of 2020 but if there is no deal to ensure no hard border in Ireland and a political declaration outlining future relations, then there will be no so-called transition period.
The situation was not helped by the emergence of a report that Trade Secretary Liam Fox was planning to slash food standards after Brexit to give the United Kingdom a competitive advantage and secure a USA trade deal.
By that time the leaders had already been through a scratchy four-hour debate on the migration crisis - a bigger concern than Brexit for many of them.
'So don't worry. Be happy, don't worry.' Mrs May was buoyed ahead of the talks when the EU's chief Brexit negotiator Michel Barnier said he hoped a deal could be sealed in six to eight weeks.
"Unfortunately we can not at this stage exclude a no-deal - it depends on both sides of negotiations".
"The Chequers plan can not be take it or leave it", Macron said.
Prime Minister Theresa May's "humiliation" at the hands of European Union leaders who rejected her Brexit plans dominated Britain's front pages Friday, although eurosceptic publications accused her tormenters of mafia-style behaviour.
She needed to return with an acknowledgement from European leaders that her domestic critics were wrong and that they would accept Chequers as a basis for meaningful talks on a future relationship.
Mr Tusk, the European Council president, publicly dismissed her carefully crafted plan a the two-day summit, telling reporters that despite having some positive elements the blueprint "will not work".
German Chancellor Angela Merkel said there could be "no compromise" on the integrity of the single market, the bloc's economic free-trade zone.
Mrs May now faces calls to abandon the Chequers plan completely from many within her own party who were unhappy with it in the first place.
"That is the best way to protect jobs here and in the European Union and to avoid a hard border between Ireland and Northern Ireland, while respecting the referendum result and the integrity of the United Kingdom".
The French president hit out at the likes of Farage, Johnson, and Rees-Mogg in a press conference at the end of the Salzburg summit of European leaders.
"Tusk said a Brussels summit on October 18 would be a "moment of truth" to overcome remaining big problems and leaders penciled in the weekend of November 17-18 to formalize a final agreement". The Dutch prime minister just stood... and said the Netherlands is better prepared for no deal than the UK.
However, at her own news conference, she appeared shaken by a barrage of questions about the EU's explicit rejection of the main pillars of her Chequers plan.
May said that leaving with no deal remains an option.