Hi there SamC4,
It's awesome that you have the opportunity to host an online workshop for your business and that people from across the country can join in. I know precision is essential when it comes to charging your customers and this kind of situation can make things a bit tricky. I'll guide you to some resources to find the answer to your question about which provincial rate to charge or if one is needed at all.
These situations provide the perfect opportunity to brainstorm and connect with others. The QuickBooks Community is a great place to do that, and you may yet receive insight from other business owners or even accountants who may be able to help. As a member of the QuickBooks Team, I'm not trained in accounting, so I can't advise on which rates to charge, if at all. What I can do is make sure you have sources you can consult to figure this out.
The first resource I recommend is the CRA. I've pulled a few pages from their website that I think may help you out, so feel free to check these out.
Apart from the CRA, an accountant is a good professional to have on your side as a business owner or bookkeeper. An accountant is trained to know the whens and hows for recording transactions, so their advice is invaluable for these kinds of situations and others. At QuickBooks, we know this is the case, which is why we've made it easy to connect with an accountant right in the software.
Using the My Accountant tab, you have the opportunity to invite an accountant you're already working with on as a user so they can help out directly in your books. The other option is the Find a pro to help button, which takes you to our directory of QuickBooks-certified accountants near you.
That should get you on your way. Take care and enjoy your week!