Gillian Sisley — you shouldn’t have to pay that. Canada has a treaty agreement with the US. (other countries do, too, including the UK) But to prevent being charged the extra 30%, you need to complete Article III of the W-8BEN and click “claim treaty agreement”. I had the exact same thing happen on Creative Market and once I filled in the W-8BEN form, the 30% became 0%.
I wish they did a better job of providing the information instead of creating such confusion. I read on FB that at least one person already deleted her account because of it, when submitting the W-8BEN would have eliminated the issue.
I will try find more complete info and share it. :)