Good question that is weird indeed. I believe the fiscal postion should also be determined according the point of sale. One of the main reason should be because of the way the GST is being calcultated can be very different weither you are looking from a B2C perspective or a B2B. On one side you want the GST to be included in the public price on the other side you only care about the price before applying GST and the only way to do this is to have different taxes categories in the accounting. Some that include GST in the final price and others that add GST on top of the B2B price. Arthur did you finaly find a way to handle the problem ?

This could also be applicable if a customer holds a 'Native Status' card, in which case the tax collection is different than your average customer.