you need to give the buyer:

the Used Vehicle Information Package
a signed Bill of Sale with your name, the buyer’s name, the date and purchase price
a completed and signed Application for Transfer — this is found on the back of an ownership permit, under the vehicle portion
a certificate that verifies the vehicle meets safety standards (if required)
​you will need to get this from a licensed mechanic
look for a green and white sign with “Ontario Motor Vehicle Inspection Station” on it
You keep:

your licence plates (because plates travel with a driver, not a vehicle)
the “plate portion” of your permit (ownership)
you will need this if you want to register your plates on another vehicle