In addition to the tax payments described in question number 21, taxpaying teams have the following restrictions. Note that most of these restrictions aren't triggered unless the team would be over the "apron" -- the point $4 million above the tax level -- following a signing or trade.
1) Teams above the apron cannot use the Bi-Annual exception (see question number 25).
2) Teams above the apron have a smaller Mid-Level exception (see question number 25). Teams above the apron can offer contracts no longer than three years, while other teams can offer four. The starting salary is also lower (for example, in 2011-12 it is $3 million for teams above the apron, versus $5 million for other teams).
3) Taxpaying teams can acquire less salary in a simultaneous trade (see question number 82).
4) Starting in 2013-14, teams above the apron cannot receive a player in a sign-and-trade transaction (see question number 89).
5)Teams above the apron do not have the same protections under the Gilbert Arenas provision (see question number 44). Under the Arenas provision other teams can offer restricted free agents salaries starting at the Non-Taxpayer Mid-Level exception. If a team with the right of first refusal does not have Early Bird rights to the player and is over the apron, it will have only the smaller Taxpayer Mid-Level exception at its disposal, and cannot match an offer for the full Non-Taxpayer Mid-Level exception.