Canadian tax liability depends on residence rather than citizenship or PR status, although PR status may be one thing they take into consideration in determining your residence for tax purposes. The more important factor is whether or not you had "residential ties" with Canada when you earned the income. The definition of "residential ties" is not always clear, but CRA lists a few things that might constitute residential ties, like having a spouse or dependents in Canada, maintaining a residence in Canada and/or having a vehicle registered there. Obviously, if you are living in Canada than your income is probably subject to Canadian tax.