Good question - I'm actually not quite sure about this. I believe that, if you were to use a commission plan with a flat rate dollar amount when selling items in GBP, the amount your entered in the "Fixed($)" field would be assessed in GBP without any conversion. For example, if you entered $5.00 in that field, GBP 5.00 would actually be charged.
I'm going to see if I can get an answer to this from our engineering team and I'll update this thread when I hear back from them. Regardless, it would be good if we could specifically support multiple currencies or at least add a note to the commission plan page describing how this works.
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