Rangers completed the signing of Belgium Under-21 international Nicolas Raskin ahead of the final evening of the transfer window.
The 21-year-old midfielder joined from Standard Liege for an “undisclosed fee on a long-term contract, subject to a work permit being confirmed”.
Raskin told the Rangers website: “I feel very excited to be here and I also feel very proud to join a very big club. I’m looking forward to playing at Ibrox. It was very exciting when I was told of Rangers’ interest because it’s a big club.”
Celtic manager Ange Postecoglou earlier ruled out any deadline-day signings, but there could be a handful of departures from Parkhead.
South Korea striker Oh Hyeon-gyu was Celtic’s fourth and final purchase of the month and discussions were ongoing over the likely exit of Giorgos Giakoumakis.
“There won’t be any other incomings,” Postecoglou said. “In terms of outgoings there are still some things happening in the background but nothing confirmed yet.”
The likes of Yosuke Ideguchi and Oliver Abildgaard could move on.
The Celtic manager said: “We have already brought in players to insulate us if guys who have not played a lot of football for us find other opportunities. It has to suit all parties obviously. We will see what happens over the next few hours.
“Anyone who is playing football and has been a meaningful contributor won’t be leaving in this window. Potentially the ones who leave are ones who haven’t had a lot of regular game time. There are four or five in the squad, I am not going to talk about individuals.”
Aberdeen have made two signings, adding 22-year-old Ajax goalkeeper Jay Gorter on loan and 30-year-old defender Angus MacDonald on a deal until the end of the season.
St Mirren manager Stephen Robinson is set to be reunited with his former Motherwell striker Tony Watt on a loan deal from Dundee United.
Robinson could also strengthen his midfield, with Ethan Erhahon on his way to Lincoln for a fee of about £300,000 and 17-year-old playmaker Dylan Reid set for Crystal Palace in a six-figure deal.
St Johnstone have landed Dundee striker Zak Rudden on loan and could add more newcomers.
Manager Callum Davidson said: “The chairman has been fantastic, he has backed me to get players, but I will only bring them in to improve the squad. We have had a few knockbacks but we will still be trying to 12 o’clock tonight.
“There possibly could be a couple of players going out. It is important we keep the freshness.”
Hearts manager Robbie Neilson feels it will be difficult to complete any late transfers.
“We’re interested in a number of players, but it’s very quiet at the minute so we’ll see how the last 12 hours go,” he said. “There’s a couple we’re looking at, but it’s late in the window. We’re trying but it will be difficult.
“I’d like to add one more, but the key thing is they have to be at a level that’s going to improve the squad and are not just coming in as a number.”
Neilson, who would not comment on the chances of an immediate move for Sheffield Wednesday’s Callum Paterson, added: “Unless anyone comes in that’s paying us big money, then nobody will be going anywhere.”
Motherwell have sold defender Sondre Solholm to Odds BK for an undisclosed fee and Connor Shields has been linked with a move to Queen’s Park, while manager Steven Hammell is looking to add to his squad.
“We are hoping to do a little bit of business, maybe some ins and outs,” he said. “It’s always moving. We thought we had something done late on Monday night and then it turns out it’s maybe not. I think we need one or two, I think we need a bit of freshness.”
Hibernian reportedly turned down offers from Wigan for striker Kevin Nisbet and midfielder Josh Campbell on Monday. Hibs boss Lee Johnson is still looking for another defender after signing 20-year-old CJ Egan-Riley on loan from Burnley on Monday and reports claim he saw a bid for Swindon and Wales midfielder Jonny Williams turned down.
Dundee United head coach Liam Fox is set to replace Watt but he refused to speculate on what a sell-on fee for Harry Souttar’s prospective £15million move from Stoke to Leicester would mean for him.
Kazeem Olaigbe has left Ross County following a loan spell from Southampton while Livingston confirmed the departure of Josh Mullin, who has been on loan with Ayr.
Kilmarnock manager Derek McInnes is keen to sign an attacking player after bringing in 18-year-old Liverpool left-back Luke Chambers on loan on Monday.