The NBA's salary cap is famously known as a "soft cap," allowing teams to surpass the cap threshold using various cap exceptions, sometimes by a significant margin. Last season, the Lakers' team salary exceeded the cap by $40MM, with the team spending about $100MM (plus taxes) on its roster of players.
However, under the league's Collective Bargaining Agreement, there are a few instances in which a team can become hard-capped for a season. If a team's salary exceeds the luxury tax threshold ($71,748,000) by $4MM+, that team is not permitted to acquire a player via sign-and-trade, or to use the full mid-level or bi-annual exceptions. As soon as a team completes a sign-and-trade deal, or uses its BAE, or uses more than $3,182,700 of its MLE to sign a player, that club becomes hard-capped at $75,748,000 for the 2013/14 season. In other words, team salary can't exceed that amount at any point before June 30th, 2014.
For some clubs, that hard cap isn't a major concern. For instance, the Pelicans still have about $12MM in breathing room below the hard cap, and seem to be just about done making moves. On the other hand, the Celtics are only about $2MM below the hard cap, so any trades or signings Boston makes for the rest of the season will have to be constructed to ensure team salary doesn't surpass that $75.748MM cutoff.
Here are the clubs who are now locked into a hard cap for the 2013/14 season, along with an estimation (via HoopsWorld) of their current team salaries and the reason(s) why the hard cap was created:
Current estimated team salary: $73,638,001
Hard cap created: Acquired Keith Bogans via sign-and-trade
Los Angeles Clippers
Current estimated team salary: $72,361,060
Hard cap created: Acquired J.J. Redick via sign-and-trade; signed Matt Barnes and Darren Collison via non-taxpayer MLE
Current estimated team salary: $70,710,039
Hard cap created: Acquired Quentin Richardson via sign-and-trade
Current estimated team salary: $69,883,992
Hard cap created: Signed Martell Webster via non-taxpayer MLE; signed Eric Maynor via BAE
Current estimated team salary: $69,150,000
Hard cap created: Signed C.J. Watson via BAE
Golden State Warriors
Current estimated team salary: $68,333,105
Hard cap created: Acquired Andre Iguodala via sign-and-trade; signed Marreese Speights and Toney Douglas via non-taxpayer MLE
Current estimated team salary1: $66,849,937
Hard cap created: Acquired Randy Foye via sign-and-trade; signed J.J. Hickson via non-taxpayer MLE; signed Nate Robinson via BAE
San Antonio Spurs
Current estimated team salary2: $64,782,127
Hard cap created: Signed Marco Belinelli and Jeff Pendergraph via non-taxpayer MLE
New Orleans Pelicans
Current estimated team salary: $63,347,645
Hard cap created: Acquired Tyreke Evans via sign-and-trade
Current estimated team salary3: $61,158,583
Hard cap created: Acquired Kevin Martin via sign-and-trade; signed Corey Brewer via non-taxpayer MLE; signed Ronny Turiaf via BAE
1 Estimate includes Timofey Mozgov's cap hold
2 Estimate includes Gary Neal's cap hold
3 Estimate includes Nikola Pekovic's cap hold
HoopsWorld was used in the creation of this post.