If you are a freelance worker or a self-employed individual, you file your taxes as if you are a small business owner which means for that portion of self-employed income, you report that income, subtract your business expenses related to earning that income, and then report the remainder as your earned income for the year.
In addition to your general income tax return, you must complete and submit form T2125, Statement of Business and Professional Activities. This form helps you to calculate your income and deductions related to business-use-of-home and vehicle expenses.
When you file your taxes, keep records for all of your income and expenses. If you need to destroy those records, submit form T137.
Additionally, if you have employees or need to submit GST/HST payments, you must apply for a business number (BN) and open up a payroll number (RP) or a GST/HST number (RT). You can do that online, but make sure once you register, that you file up to date.