My company is a US Delaware C Corp. I want my app to be available in Canada as well as US. If I plan to introduce a subscription service, do I have to file income tax in Canada as well? I know Apple collects and pays Sales Taxes for us. I would think since Apple pays us in the US, I would only need to care about US taxes. Is this correct?
Taxes, especially where borders are concerned, are always tricky. The rules can be different for different people. You will need to find a competent accountant and/or tax attorney.
This isn't just a cop-out answer either. You specifically asked about a Delaware corporation and Canadian taxes. Delaware is known as a place to create US-based companies in name only. And it's odd to ask about Canada since there are so many other more important and more problematic tax regions in the world. I'm guessing that there might be specific reasons why you are asking this specific question. Therefore, you need someone with specific answers for you.
