This is interesting to me personally since I teach at Ontario colleges (which are currently on strike --- I'm on lay-off due to the fact that I teach too many hours to be in the union).  To make ends meet in one year I often teach at multiple colleges (depending upon the semester) and I've been billing trough my consulting firm whenever possible.  I and others have recently been told that all future work will have to be through a T4 because of rule changes by the CRA.

I don't know i that is true or not.  The management at the colleges love to play games with the rules.