[AFMUG] Calculating USF

[Simon Westlake]

I seem to vaguely remember someone once telling me it is calculated as a 
percentage of the tax that you assess your customer, but that doesn't 
seem right to me. Googling has proved fruitless. Anyone here collect USF 
and, if so, how do you calculate it? Or even if you don't collect USF 
but know how it should be done, that'll work too!