I know this has been suggested before and it has been rejected, however, I think Mike should really reconsider increasing taxes. As a player, your money is always going up, rarely going down, this creates a boring feeling that what you have is granted and there's no way to lose it, which makes it feel cheap, and make many players lose motivation to play.
The taxes would take a certain % cut of all your daily income every game day, according to income brackets.