If your business/employment has more than one activity, use the code that most closely describes your main activity. For instance, if your main activity is youtube then you must use the code 519130 which is Internet Publishing and Web Search Portals. Whereas, if your main activity is affiliate marketing then you must use the code 541611 which is Administrative management and general management consulting services. I suggest you to check the CRA's list of industry codes for self-employment, and select one that closely resembles to your main activity.
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