Canadian investors need to be aware of 15% tax that the US government charges Canadian investors who hold US equities in non registered accounts other than retirement accounts such asRRSP. For example, if you hold 1000 shares of AAPL in your TFSA account and earn approximately 1000 $ in dividends for the year, $150 will be withheld by the US government. So, you will receive only $850 dividends.

You can talk to your accountant to see how to mitigate the loss here when you file your taxes.