Rafa Benitez has named the date at Newcastle United.
Benitez – who has spoken to owner Mike Ashley about the January transfer window – wants the club to do its business by January 20.
Speaking ahead of this afternoon's game against West Ham United at the London Stadium, United's manager stressed the need to "do things as quickly as possible".
“It's really important to do that," said Benitez, who is close to securing Chelsea winger Kenedy on a season-long loan.
"We haven't received any offers for any of our players at this stage, but we have to do things as quickly as possible, and I have the belief and the confidence in (Newcastle owner) Mike Ashley that by January 15 or 20, we have to be there with everything done."
Newcastle are 18th in the Premier League table after losing eight of their last nine games.
United are away to league leaders Manchester City on January 20.
The fixture is followed by important games against Burnley and Crystal Palace.
Asked about his proposed deadline, Benitez added: "You have to have some time (to work with players). If you go to January 30, it's always very difficult to do business in the last day. You have to do business early and get players as soon as possible."