In professional football, a transfer is the action taken whenever a player under contract moves between clubs. It refers to the transferring of a player's registration from one association football club to another. In general, the players can only be transferred during a transfer window and according to the rules set by a governing body. Usually some sort of compensation is paid for the player's rights, which is known as a transfer fee. When a player moves from one club to another, their old contract is terminated and they negotiate a new one with the club they are moving to, unlike in American, Canadian and Australian sports, where teams essentially trade existing player contracts. In some cases, however, transfers can function in a similar manner to player trades, as teams can offer another player on their squad as part of the compensation.
The concept of a football transfer first came into existence in England after The Football Association (FA) introduced player registration sometime after 1885. Before that, a player could agree to play one or more games for any football club. After the FA recognised professionalism in 1885, it sought to control professional players by introducing a player registration system. Players had to register with a club each season, even if he remained with the same club from the season before. A player was not allowed to play until he was registered for that season. Once a player was registered with a club, he was not allowed to be registered with or play for another club during the same season without the permission of the FA and the club that held his registration. The players however, were free to join another club before the start of each season, even if their former club wished to retain them.
Sometime after the Football League was formed in 1888, the Football League decided that restrictions had to be placed on the ability of richer clubs to lure players from other clubs to prevent the league being dominated by a handful of clubs. From the start of the 1893–94 season onwards, once a player was registered with a Football League club, they could not be registered with any other club, even in subsequent seasons, without the permission of the club he was registered with. It applied even if the player's annual contract with the club holding their registration was not renewed after it expired. The club was not obliged to play them and, without a contract, the player was not entitled to receive a salary. Nevertheless, if the club refused to release their registration, the player could not play for any other Football League club. Football League clubs soon came to realize that they could demand and earn a transfer fee from any other Football League club as consideration for agreeing to release or transfer the player's registration.