Most businesses in Ontario that employ workers (including family members and sub-contractors) must register with the Workplace Safety and Isurance Board (WSIB) within 10 days of hiring their first full- or part-time worker. It's the law.
Visit the Workplace Safety and Insurance Board at the following site for more information:
http://www.wsib.on.ca/wsib/wsibsite.nsf/public/home_e