You must comply with both U.S. and Canadian filing requirements. In the United States, you generally are required to file a return if you have income from the performance of personal services within the United States. However, under certain circumstances, that income may be exempt from payment of U.S. tax pursuant to the U.S.-Canada income tax treaty. You need to determine what type of visa you have, and how that impacts your residency status in the United States. If, based on the tax code and your visa status you are treated as a U.S. resident, then your entitlement to treaty benefits will be impacted. You must contact the Canadian government to determine whether you must file a Canadian tax return and pay Canadian taxes.

References:

• Publication 519, U.S. Tax Guide for Aliens
• Publication 597, Information on the United States-Canada Income Tax Treaty
• Publication 901, U.S. Tax Treaties