You will file his taxes, he being self-employed. If you're a sole proprietor or self-employed, you must fill out your T1 General, which is your standard personal income tax return. You must also complete a separate T2125 “Statement of Business or Professional Activities.” This is where you specify: Business and professional income earned.
Refer to this TurboTax article for step-by-step instructions: Self-Employed Tax Return Canada – T2125 Step by Step ...
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