Everton announced the signing of teenage defender Niels Nkounkou on a free transfer this week after he left Marseille.

The deal was announced on Thursday lunchtime but was completed on Wednesday night as the Blues faced Leicester City at Goodison.

So how have Everton been able to sign Nkounkou when the transfer window is not yet open?

The Premier League were given special dispensation to open the window on July 1 - but only for 24 hours - in order for clubs to register new players where agreements had been reached.

Chelsea, for example, have been able to register new recruits Timo Werner and Hakim Ziyech, and the one day window allowed Everton to officially confirm Nkounkou as an Everton player for the 2020-21 season.

Manchester City were able to ratified the signing of Pablo Moreno from Juventus, Man United have officially extended Odion Ighalo's loan for next season and Newcastle completed the free transfer of Mark Gillespie from Motherwell.

FIFA allows leagues two transfer windows per season, lasting no more than 16 weeks in total, with the first window capped at 12 weeks.

The dates for the opening of this summer's window have yet to be determined but given FIFA are advising that transfer periods end by October 5.

It is expected that the Premier League window will re-open, following the one day window earlier this week, at the end of the month.

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It has been reported that the next Premier League meeting will be convened on Thursday, where the transfer window will be discussed.

Everton are hoping to make two or three senior signings this summer.