The Black Cats are firmly in the race for automatic promotion from League One, yet the squad does appear a little light in some areas.
There are also plans for some of the squad's younger players to leave on loan, with other outgoings also possible.
Sunderland’s rivals will also be looking to strengthen in the final days of the transfer window.
Here are the deals which have been completed so far in League One:
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1. Accrington Stanley
IN: Rosaire Longelo (Newcastle, undisclosed), Jay Rich-Baghuelou (Crystal Palace, undisclosed) | OUT: Dion Charles (Bolton) Photo: Lewis Storey
2. AFC Wimbledon
IN: Terry Ablade (Fulham, loan), Tomas Kalinauskas (Barnsley, loan) | OUT: Corie Andrews (Colchester, loan) Photo: Alex Davidson
3. Bolton
IN: Dion Charles (Accrington, £320K), Marlon Fossey (Fulham, loan), Aaron Morley (Rochdale, £100K), James Trafford (Man City, loan), Jon Dadi Bodvarsson (Millwall, free) | OUT: Ali Crawford (St Johnstone), Eoin Doyle (St Patrick's Athletic), Harry Brockbank (released), Dennis Politic (Cremonese) Photo: Charlotte Tattersall
4. Burton
IN: William Kokolo (Middlesbrough, undisclosed), Gassan Ahadme (Norwich, undisclosed) | OUT: Michael Bostwick (Stevenage, loan), Omari Patrick (Carlisle), Kane Hemmings (Tranmeme) Lucas Akins (Mansfield) Photo: Tony Marshall