While the transfer windows are open, clubs may change their squads as many times as they want. However they will only be able to make alterations outside the windows if there are exceptional circumstances and the changes are approved by the Premier League board.
For example, if a club has two out of three goalkeepers injured they may be permitted to bring in a replacement under the guidelines drawn up by a specially formed working party.
Players in the 25-man squads who go out on loan to Football League clubs may not be replaced. However they may reclaim their place on their return.
Clubs do not have to name a full squad of 25 if they do not have that many contracted players and in this instance they may add free agents outside the transfer window. However if they have 25 eligible contracted players, they must be named.