The majority of club managers like to complete their transfer business in the summer, but the January window provides the perfect opportunity to strengthen at the midway point.
So, what is happening at the moment? Here, Sports Mole has gathered all the latest news and speculation.
This evening's headlines:
Liverpool confirm Steven Gerrard exit
Liverpool confirm that club captain Steven Gerrard will leave the team at the end of the 2014-15 Premier League season.
Report: Juventus join Wesley Sneijder race
Juventus reportedly emerge as leaders in the race to sign Dutch international Wesley Sneijder from Galatasaray during January's transfer window.
Sylvan Ebanks-Blake joins Preston North End
Preston North End announce that Sylvan Ebanks-Blake has joined the side until the end of the 2014-15 season following a trial at the club.
Swansea City complete Matt Grimes signing
Swansea City finalise a deal to take Exeter City midfielder Matt Grimes to the Liberty Stadium.
Nathaniel Chalobah ends loan spell with Burnley
Burnley manager Sean Dyche reveals that midfielder Nathaniel Chalobah has returned to parent club Chelsea.
Report: Stoke City want Aaron Lennon on loan
A report claims that Stoke City want to sign Tottenham Hotspur midfielder Aaron Lennon on loan in January.
Derby County sign Darren Bent on loan
Derby County sign Darren Bent on loan from Aston Villa until the end of the season.
Report: Manchester United preparing £70m Paul Pogba bid
A report claims that Manchester United are willing to pay £70m to bring Juventus midfielder Paul Pogba back to Old Trafford this summer.
Tomas Kalas to join Middlesbrough on loan?
A report claims that Chelsea defender Tomas Kalas will join Middlesbrough on loan for the rest of the season.
Report: Lukas Podolski close to Inter Milan loan
A report claims that Arsenal forward Lukas Podolski will travel to Milan on Friday evening to conclude a loan deal with Inter Milan.
Bayern Munich sign Joshua Kimmich
Bayern Munich sign promising midfielder Joshua Kimmich from Stuttgart.
Report: Manchester United, Chelsea want Raphael Varane
A report claims that Manchester United and Chelsea will battle for the services of Real Madrid centre-back Raphael Varane.
Report: Tottenham Hotspur after James McCarthy
A report claims that Tottenham Hotspur want to sign Everton midfielder James McCarthy in January.
Dani Alves: 'My future can wait'
Barcelona defender Dani Alves claims that he will not decide his long-term future this month.
Report: Arsenal want Loris Karius
A report claims that Arsenal want to sign Mainz 05 goalkeeper Loris Karius in January.
Keith Millen: 'Crystal Palace have no plans to sell'
Crystal Palace caretaker boss Keith Millen insists that the club will keep hold of their key players this month.
Matt Law
