http://members.cox.net/lmcoon/salarycap.htm#Q36" Restricted free agency exists only on a limited basis. It is allowed following the fourth year of rookie "scale" contracts for first-round draft picks (see question number 41). It is also allowed for all veteran free agents who have been in the league three or fewer seasons. However, a first round draft pick becomes an unrestricted free agent following his second or third season if his team does not exercise its option to extend the player's rookie scale contract for the next season. All other free agency is limited to unrestricted free agency.
In order to make their free agent a restricted free agent, a team must submit a qualifying offer to the player by June 30. This prevents the team from not offering a contract and waiting to swoop in when the player tries to sign elsewhere. The qualifying offer ensures that the team does not gain the right of first refusal without also offering a contract themselves. The amount of the qualifying offer for players on rookie "scale" contracts is based on the player's draft position (see question number 41). The qualifying offer for all other players must be for 125% of the player's previous salary, or the player's minimum salary (see question number 11) plus $175,000, whichever is greater. The qualifying offer must be for one season. A player can elect to accept his qualifying offer (the qualifying offer must be accepted by March 1) and play the following season under its terms. This is sometimes done in order to become an unrestricted free agent the following summer (see question number 38).
A qualifying offer cannot be accepted after March 1. Teams may place a shorter time limit on their qualifying offer, specifying any date between October 1 and March 1 by which it must be accepted. If the deadline passes and the qualifying offer is neither withdrawn nor accepted, then the player continues to be a restricted free agent. The team and player are also still free to negotiate a new contract after the qualifying offer ends -- the deadline only affects the player's ability to accept the qualifying offer.
Teams may also withdraw an outstanding qualifying offer in which case the player becomes unrestricted. This happened with Toronto and Keon Clark in 2002. The qualifying offer cannot be withdrawn after July 23 without the player's approval. "