IANAL, but I recommend that you keep track of how many days you were in the US each month, and how many of those days were for work. It's likely that an account

IANAL, but I recommend that you keep track of how many days you were in the US each month, and how many of those days were for work. It's likely that an accountant or tax professional will ask you for that information to support your claim of tax residency in Canada.