Hi Shotgun Pete. Thanks for your reply.
It turns out commission income from non-Canadian or non-registered affiliate programs is considered online advertising revenue and is therefore zero-rated. You still have to be registered for GST if you earn more than $30k (that’s per year, not per month) but you don’t charge GST unless they are GST registered which *I think* normally means that they have some kind of Canadian presence – even if its just a sales or service office.
I wouldn’t expect any casino, bingo or poker sites to be GST registered – but with other affiliate programs it’s worth double checking.
It is not necessary to get a ruling if your income is entirely from affiliate programs and advertising – but you do need to register and report.