How can footballers be signed outside of the transfer window? Rules explained as Chelsea’s Oscar heads to Shanghai SIPG

CHELSEA and Shanghai SIPG have agreed terms for midfielder Oscar to move to the Chinese Super League club.

Already, pictures of the 25-year-old Brazilian holding the shirt have been circulated - but he cannot officially join the club until the start of the January transfer window.

Here we explain the rules of transfer windows and movement of players around the world.

How can footballers be signed outside of transfer windows?

Players under contract cannot be actually signed until the window opens - so Oscar's official paperwork and registration may well be done the moment it opens in the UK on 1 January.

There will be other agreements that can be signed between the two clubs, and given the money at stake, is it unlikely Chelsea will pull the rug from under Shanghai's feet.

But deals go on behind the scenes all the time throughout the campaign and particularly leading up to January and in the summer off-season.

In the summer, you will often see players signed, but they will not move until 1 July when the window opens, as that is when their contract will expire at their previous club.

It is unclear why Oscar was announced now - but it is most likely due to both clubs wanting to get the furore out of the way before everything hots up next month.

If a footballer is a free agent, he can still sign for a club in the off-season, especially in the lower leagues where that has happened a lot recently due to the emergency loan window being scrapped.

But that cannot happen in the Premier League, where for example Joey Barton, who re-joined Burnley after having had his contract terminated by Rangers, has to wait until January to play despite signing this week.

Does it make a difference signing from one continent to another and is everyone's transfer windows the same? 

No it does not. It does not matter if a team under UEFA's jurisdiction such as Chelsea sell a player to an Asian team like Shanghai who operate under the Asian Football Confederation (AFC).

Players often have to get work permits to play in a particular country, as well as international clearance, but that is usually taken care of by agents.

What is boils down to is the differing transfer windows in particular regions. So while in Europe, transfer windows will be roughly the same from nation to nation - give or take a day or so - due to our seasons running from summer to summer, in Asia it is different.

Their league starts in early March, so their winter transfer window begins at the start of January and ends at the end of February - so they can splash the cash for a month longer than Premier League teams can, but will not be able to immediately sign a player from a European league after our window closes.

When are the English transfer windows?

Our summer transfer window usually runs from the beginning of July, and closes at the end of August. But as stated, negotiations go on the whole time behind the scenes.

Our winter one opens on January 1 and closes at the end of the month, and it is usually harder to sign big players are they are in the middle of their contracts, or in the middle of their season when things are at stake.

But clubs are more on guard, to not sell their best asset or to bring someone in desperately who can turn the fortunes of their season around.

Rules are strict on players movements, so in the case of Oscar , him joining in January is down to our window - it opens on 1 January, so that is when he will officially be allowed to leave.