Each Premier League club submit a squad list after each transfer window closes.
It can contain no more than 17 players who do not fulfil "Home Grown Player" criteria.
The remainder of the squad, up to a total of 25 players, must be home grown.
Changes to the squad list may be made during the period of a transfer window.
A "Home-Grown Player" means a player who, irrespective of nationality or age, has been registered with any club affiliated to The Football Association or the Football Association of Wales for a period, continuous or not, of three entire seasons, or 36 months, before his 21st birthday (or the end of the season during which he turns 21).
Under-21 players are eligible over and above the limit of 25 players per squad.
Each player is assigned a squad number, which they wear during Premier League matches.
For the 2018/19 campaign Under-21 players will have been born on or after 1 January 1997.
The latest squad lists can be viewed here.