Extract from the Income War Tax Act, 1917
(7-8 George V, Chap. 28)

[One consequence of the First World War was a great increase in direct taxation. Until 1914 the Dominion drew its revenue largely from customs and excise duties. But during the conflict and in the postwar years various "war" taxes were imposed to meet the enormous new expenditures the war involved. Some of these became permanent features of the taxation system. This was notably the case with the income tax, first introduced in 1917, and the sales tax, introduced in 1920. In 1921, for the first time, revenue from the new direct taxes exceeded that from customs duties.]

Assented to 20th September, 1917

4. (1) There shall be assessed, levied and paid, upon the income during the preceding year of every person residing or ordinarily resident in Canada or carrying on any business in Canada, the following taxes:-
(a) four per centum upon all income exceeding fifteen hundred dollars in the case of unmarried persons and widows or widowers without dependent children, and exceeding three thousand dollars in the case of all other persons;
and in addition thereto, (b) two per centum upon the amount by which the income exceeds six thousand dollars and does not exceed ten thousand dollars; and, (c) five per centum upon the amount by which the income exceeds ten thousand dollars and does not exceed twenty thousand dollars; and,
(d) eight per centum of the amount by which the income exceeds twenty thousand dollars and does not exceed thirty thousand dollars; ….