The bonus rule was a rule instituted by Major League Baseball in 1947 to prevent teams from assigning certain players to farm teams. The rule stipulated that when a major league team signed a player to a contract with a signing bonus in excess of $4,000, the team was required to keep that player on their 25-man active roster for two full seasons. Any team that failed to comply with the rule lost the rights to that player's contract, and the player was then exposed to the waiver wire. Once a player remained with the team for two full seasons, he could be assigned to a farm team without repercussions.

In sports, a farm team, farm system, feeder team, feeder club, or nursery club is generally a team or club whose role is to provide experience and training for young players, with an agreement that any successful players can move on to a higher level at a given point, usually in an association with a major-level parent team. This system can be implemented in many ways, both formally and informally. It is not to be confused with a practice squad, which fulfills a similar developmental purpose but the players on the practice squad are members of the parent team.