Do I understand correctly that you will be filing taxes in Canada as a non-resident?
Talks to your accountant again.
There is a tax treaty between the U.S. and Canada, where you get credit for taxes paid to the U.S.
The answer to your question is that your accountant is correct. As a non-resident this is Part III income and you are subject to Part III tax of 25 percent\. (Unless a tax treaty allows you to treate it differently).
I understand that you are Canadian and this is money that you pay into Canada.
But Canada consider's you a non-resident, AND the U.S. Taxes you as a permanent resident or U.S. Citizen. The U.S. asks that you report world wide income, unless specifically excluded by treaty.
I think you and you accountant may mis-handling your taxes. I am not arguing that you do not report this income in the U.S., or how you are doing it. It may be more beneficial for you to report this on U.S. taxes.
Pehaps I should not be opening that can of worms. But I want to make sure you are getting the best treatment as you can for your taxes.
Here are two documents that you should look at:
Thanks, XXXXX XXXXX welcome. best of luck to you.