There's various high-profile and long-running sagas still to be finalised, including: Can Arsenal keep hold of Alexis Sanchez? Is Monaco about to lose three more of their star players? Will Barcelona buy another forward to replace Neymar?
Here's a country-by-country look at the major talking points heading into the final hours of Europe's transfer window.
It has been a record-breaking transfer window in the Premier League, with clubs using money received from bumper broadcast deals to spend 1.2 billion pounds (A$2 billion) on players so far. Many teams are still in the market, though.
The future of Alexis Sanchez has been a slow-burner but is likely to be the biggest story.
Manchester City have been linked heavily with the Chile forward and reportedly made a bid of 50 million pounds (A$82 million), even though he has only one year left on his Arsenal contract.
City could also sign a center back, potentially Jonny Evans from West Bromwich Albion despite having two bids rejected already.
Liverpool has refused to enter negotiations with Barcelona for playmaker Philippe Coutinho, but will the Reds maintain their "not for sale" stance?
Monaco winger Thomas Lemar and Southampton defender Virgil van Dijk have also been targets for Liverpool.
Versatile Arsenal midfielder Alex Oxlade-Chamberlain is set to complete his move to Liverpool on Thursday.
Premier League champions Chelsea want to offload Diego Costa, after the striker was told by manager Antonio Conte that he does not feature in the club's plans.
Midfielders Riyad Mahrez and Danny Drinkwater could leave Leicester after handing in transfer requests.
Of the top teams, only Manchester United is likely to be quiet on Thursday.
The transfer window in Spain closes a day later than in most leagues, giving clubs extra time to try to make deals.
Barcelona is still trying to sign Philippe Coutinho from Liverpool, despite three rejected offers, in what would be another blockbuster addition after the arrival of Ousmane Dembele from Borussia Dortmund to replace Neymar.
Aside from interest in Coutinho, Barcelona sporting director Robert Fernandez said the club may still sign yet another player before the window closes.
Real Madrid is not apparently looking to sign anyone and Atletico Madrid is still banned by FIFA from registering any new players.
Defending champions Monaco should be careful what they wish for. Although the club is piling up profits, it is dismantling a side that thrilled Europe by reaching the UEFA Champions League semi-finals and scoring more than 150 goals.
Kylian Mbappe is set to join Paris Saint-Germain on loan with a view to a permanent signing that would make the 18-year-old forward the second most expensive player in history at 180 million euros (A$270 million).
It would also make him the latest from last season's title-winning side to leave, after attacking midfielder Bernardo Silva, left back Benjamin Mendy (both Manchester City), forward Valere Germain (Marseille), and defensive midfielder Tiemoue Bakayoko (Chelsea).
It may not end there as skillful left-sided midfielder Thomas Lemar is courting wide interest, with Liverpool reportedly bidding about 80 million euros (A$120 million) for the France international, and PSG are eager to sign defensive midfielder Fabinho as a long-term replacement for the aging Thiago Motta.
If Lemar and Fabinho are sold, it would push the figure of Monaco's export sales to nearly half a billion euros (A$752 million).
It looks like being a quiet final day of the transfer window in Italy once again, with most of the business already done by the major clubs.
AC Milan has been the biggest mover, with its new owners spending more than 200 million euros ($234 million) on players such as Leonardo Bonucci, Nikola Kalinic, Andre Silva, Ricardo Rodriguez, Franck Kessie, Andrea Conti, Hakan Calhanoglu, Lucas Biglia and Mateo Musacchio.
Defending champions Juventus have brought in Douglas Costa, Mattia De Sciglio, Wojciech Szczesny, Federico Bernardeschi and Blaise Matuidi, and could complete a deal for Schalke defender Benedikt Hoewedes.
Inter Milan are also hoping to sign another defender, reportedly Shkodran Mustafi from Arsenal, particularly fter full-back Joao Cancelo injured his knee in training with Portugal on Tuesday.
Roma is unlikely to make any more significant changes, after signing Patrik Schick from Sampdoria on Tuesday, and neither are Napoli.
Borussia Dortmund began spending the windfall earned from Ousmane Dembele's move to Barcelona for potentially 147 million euros (A$220 million) by signing Ukraine forward Andrey Yarmolenko and right back Jeremy Toljan this week.