If a team is below the cap, then their Disabled Player, Bi-Annual, Mid-Level (either the Taxpayer or Non-Taxpayer Mid-Level, whichever applies to the team) and/or trade exceptions are added to their team salary, and the league treats the team as though they are over the cap1. This is to prevent a loophole, in a manner similar to free agent amounts (see question number 38). A team can't act like it's under the cap and sign free agents using cap room, and then use their Disabled Player, Bi-Annual, Mid-Level and/or trade exceptions. Consequently, the exceptions are added to their team salary (putting the team over the cap) if the team is under the cap and adding the exceptions puts them over the cap. If a team is already over the cap, then the exceptions are not added to their team salary. There would be no point in doing so, since there is no cap room for signing free agents.
So being under the cap does not necessarily mean a team has room to sign free agents. For example, assume the cap is $58 million, and a team has $51.5 million committed to salaries. They also have a Non-Taxpayer Mid-Level exception for $5 million and a trade exception for $5.5 million. Even though their salaries put them $6.5 million under the cap, their exceptions also count toward their team salary, increasing their total to $62 million, or $4 million over the cap. So the team actually has no cap room to sign free agents, and instead must use its exceptions to sign players.
Teams have the option to renounce their exceptions in order to reclaim their cap room. So in the example above, if the team renounced their Traded Player and Mid-Level exceptions, then the $10.5 million is taken off their team salary, which then totals $51.5 million, leaving them with $6.5 million of cap room which then can be used to sign free agent(s).
