(1) If the Commissioner effects service of a document on an agent who has actual or apparent authority to accept service of the document on behalf of the agent's principal, the principal is taken, for the purposes of a taxation law, to have been duly served.
(2) If the Commissioner effects service of a document relating to a partnership on a member of a partnership, each member of the partnership is taken, for the purposes of a taxation law, to have been served.
(3) If the Commissioner effects service of a document relating to an unincorporated association on a member of the committee or management of the association, each member of the association is taken, for the purposes of a taxation law, to have been served.
(4) Subject to the regulations, if 2 or more taxpayers are jointly liable for tax, service on any one of them is taken, for the purposes of a taxation law, to be service on each one of them.