Hello passernkl,
"(1) "Foreign Slip" section under "Employment Income" and "Enter the portion of foreign income exempt under a tax treaty"? Or is this section only for the foreign income I earned after I arrived in Canada?"
This is for foreign income you earned after you became a resident of Canada
"(2) "Paid income tax to a foreign country" -> "Foreign tax credit - non-business" -> "Tax treaty exempt amount"? ***FYI- I have already done the tax clearance with my home country before I came to Canada. "
Same as (1), this is for foreign income you earned after you became a resident of Canada. You don't need to enter anything here if it is related to income you earned before you became a resident of Canada.
