A qualifying offer (QO) is a one-year contract offer a team makes to its own young free agent to make them restricted, which gives the team the right to match any other offer they sign.
In HoopSim the QO is 135% of the player's last salary, at least the minimum plus $200K and never more than their maximum. You can issue one when a player's deal ends with three or fewer years in the league or when their first-round rookie deal ends, in the Offseason wizard before free agency opens. Issue it and they are restricted, with the QO on your books as a cap hold; decline and they are unrestricted with no hold. If nobody signs them, they play the next season on the QO.
Rulebook: Restricted FA. Related: restricted free agent, cap hold.