Do I need to claim non residency foreign income in Canadian taxes and if so am I supposed to pay additional taxes despite being non resident?

As a non-resident, you will not be taxed on your foreign income in Canada. You only need to enter these amounts because they are used to calculate your eligibility for certain credits. If your refund goes down or your tax payable goes up, it's likely because the foreign income you added has reduced or eliminated those credits.

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