NBA basketball contracts are dictated by the rules outlined in the Collective Bargaining Agreement between the NBA and the NBA Players Association. All NBA basketball contracts are subject to a salary cap which regulates the maximum amount teams may pay their players. The NBA salary cap is often referred to as a "soft cap" due to the many exceptions and loopholes which allow teams to offer basketball contracts to players when their payroll exceeds the salary cap. For example, there is a salary cap exception allowing basketball teams to secure a player to replace a disabled player. Basketball contracts are often negotiated by sports agents who work on behalf of the players. Options to extend a contract are common, and special clauses and perks may also be negotiated. If a player has a guaranteed contract, that player will continue to be paid even if they are released from the team.