When does this year's January transfer window close?
The window officially shuts on Premier League clubs at 11pm on Monday 1 February in the UK - an hour after shutting in France, Germany, Italy and Spain.
Earlier this week, Spain's La Liga opted to keep its window open for an extra day beyond its initial 31 January deadline in order to bring it in line with rival leagues in Europe.
Can clubs make loan signings after the window shuts?
Once the window shuts, Premier League clubs are stuck with the squad they've got until the season ends - but Football League clubs can sign players for up to 93 days on an "emergency loan" from a week after the transfer window ends until 5pm on 24 March.
What needs to be done to get a transfer over the line?
For Fifa to ratify a transfer, it must be entered into Fifa's Transfer Matching System (TMS) before their association's deadline. The system is designed to prevent future disputes between the clubs, by ensuring the terms of a transfer match for both parties.
According to Real Madrid, United submitting the relevant paperwork to the TMS two minutes past the deadline was the reason they were unable to purchase David de Gea this summer.
Clubs often employ external legal teams to work around the clock in the final days to ensure all the terms and conditions are all tied up in time for the deadline.
So how come some deals aren't confirmed until well after the deadline?
If two English clubs are thrashing out a deal late until the night, and there are one or two complications preventing them from submitting the full paperwork before the deadline, from 9pm clubs may fill out a "deal sheet" including all the key information and confirming that a deal has been reached.
They are then until 1am to finish getting the full paperwork to the Premier League.
How many times are players allowed to move between clubs?
Players may be registered with three different clubs during the same season, but may only actually play for two.
When are players cup tied in Europe and when are they not?
A team in the Champions League or Europa League can register three new players for the knockout phase, one of whom can have played in the group stage of the other competition - i.e a Champions League team may register a player for the last 16 who played in the Europa League group stage.
What are the rules for international players who need a work permit?
New work permit rules from the FA make it harder than ever for English clubs to sign players from outside the non-EEA (European Economic Area).
Only players deemed "internationally established at the highest level" capable of making a "significant contribution" will be given work permits - and this is decided by the percentage of international matches a players has appeared in for his country over the previous 24 months (or 12 months for players aged 21 or younger).
The percentage of matches a player must have appeared in over the last two years increases the lower ranked his nation is:
|Fifa ranking||Required percentage of international matches over previous 24 months|
|1-10||30 per cent or more|
|11-20||45 per cent or more|
|21-30||60 per cent of more|
|31-50||75 per cent or more|