If you are changing ownership of a .ca domain, the change to the whois record is not processed as described earlier for all other domains, but through a "registrant transfer." The .ca whois system run by CIRA, the Canadian Internet Registry Authority, is based on registrant accounts which contain the information for the domain owners and contacts, and the same account can be responsible for a number of domains. So when the ownership of a .ca changes, rather than changing the domain's contact information you need to transfer the domain to the new owner's registrant account.

The registrant transfer must be processed by the current registrar of the domain, so the current owner will need to contact them to initiate the transfer. If the new owner has a registrant account already the registrar will only need to initiate the transfer and confirmation emails will be sent to both the current and new owners' admin contacts. Once both sides have confirmed the transfer the domain will move to the new account and the change in ownership on the whois record will be complete.

If the new owner of the domain does not have a registrant account as yet, an account will need to be created. So the new owner will have to provide the following information to the current owner.

Administrative Contact:

Name - Name of the person who will be responsible for confirming changes to the domain, and who will be the main contact for any sort of queries required by the registry or registrar.
Job Title - Title within the company that owns the domain, if applicable
Postal Address - Mailing address for the administrative contact - must be valid. PO Boxes are fine.
Phone - A valid phone number at which the admin contact can be reached.
Fax - Optional, but also very useful.
Email address - This is vital, as any changes to the account or domain must be confirmed by this address.

Technical Contact:

The same information as above. This section is required by CIRA, but is not currently used. If desired, the same information as Administrative contact can be provided.

Once this information has been provided the registrar can create the new account and the new admin contact will need to confirm it by email. The registrar can then proceed with the transfer. It should be noted that a transfer of registrant, or registrar, adds a year to the registry of the domain so the registrar will require payment for that year of registry before proceeding with the transfer of ownership.