There was no income tax in Canada till World War I.
1917 - during WW I, the Income War Tax Act imposed a 4% tax on income over $2,000 yearly for all single men; and for others on income over $3,000 but under $6,000. There was a graduated tax rate for those with incomes over $6,000.
See WarTime Canada for more about taxation in Canada during this period and World War II. Includes sample historical tax forms.
Library and Archives Canada has many records relating to income tax, including correspondence, and the tax forms and files of some individuals in their personal papers.