Every club must submit two lists of players (A and B) to their national association by 24:00CET on Thursday. The lists (which include things like shirt numbers) are then verified, validated and forwarded to UEFA. Subject to snagging, they are expected to be announced on UEFA.com on Friday.
Who can be on List A?
A maximum of 25 players, two of whom must be goalkeepers. There are a minimum of eight places reserved exclusively for ‘locally trained players’. If a club have fewer than eight locally trained players in their squad, then the maximum number of players on List A is reduced accordingly.
What’s a ‘locally trained player’?
There are two categories:
1. Club-trained players – players who were on a club’s books for three years between the ages of 15 and 21;
2. Association-trained players – players who were on another club’s books in the same association for three years between the ages of 15 and 21. No club can have more than four association-trained players among their eight nominees on List A.
What is List B, then?
A player may be registered on List B if he is born on, or after, 1 January 1995 and has been eligible to play for the club concerned for any uninterrupted period of two years since his 15th birthday (players aged 16 may be registered if they have been registered with the club for the previous two years). Clubs are entitled to register an unlimited number of players on List B during the season, but the list must be submitted by no later than 24:00CET the day before a match.
Can clubs change their squads again this season?
Yes … if they get through to the knockout stage. Ahead of the round of 16, by midnight on 1 February, clubs can register a maximum of three new players. The overall limit of 25 players on List A remains, though.
Any limitations on who is added?
Players may have played in qualifying for the UEFA Champions League or UEFA Europa League, but only one of them can have played in the UEFA Europa League group stage. Players cannot represent two clubs in the UEFA Champions League from the group stage onwards.
Is that it?
Erm, no. If a club cannot count on the services of at least two goalkeepers registered on List A because of long-term injury or illness (i.e. one that lasts 30 days), a club can temporarily replace him at any time during the season.
*Please note that this is a simplified version of the rather more lengthy regulations, which are available in full here (Article 43).