All commercial motor vehicle (CMV) operators in Ontario (including U.S. motor carriers) must have a valid Commercial Vehicle Operator's Registration (CVOR) certificate and carry a copy in their CMVs while operating in Ontario . The CVOR system monitors commercial carrier safety to improve road safety for all road users. All motor carriers (including U.S. motor carriers) must obtain and then renew their CVOR certificate either yearly or every two years based upon their safety rating in Ontario. You can find more details about obtaining, renewing or replacing a CVOR certificate on the Ontario Ministry of Transportation website.
U.S. motor carriers can obtain information on registering with Ontario at http://www.mto.gov.on.ca/english/trucks/commercial-vehicle-operators-registration.shtml