If I'm buying from a European supplier - let's say Germany, I'm located in Canada, and I sell to an Australian based customer. How do I handle sales tax? Do I pay (as a business) the German sales tax let's say it's 15% and how do I handle Australian sales tax? I've read that I don't have to add sales tax or collect sales tax when the customer is outside of my business' geographic location (outside Canada) but can I then go to the German tax authorities and claim back the 15% since my business is not in Germany?
Did your issue be solved yet? This is a tax rate setting guide in many countries https://avada.io/shopify/docs/how-set-up-tax-rates-countries-other-united-states-shopify.html.
I hope it's useful for you.
By the way, we have a complete guide for tax setting on Shopify, It's a list of useful guides on setting up tax rates and it could help you a lot.