Guardian liability: guardians, trustees or agents are liable for GST tax, interest and penalties as if the person were competent. Where business subject to tax, interest or penalty is carried on by a guardian, trustee or agent for a minor or other incapacitated person, the guardian, trustee or agent is liable to pay such tax, interest and penalty as if the minor or incapacitated person were a major and conducting the business personally, and all provisions of the Act and rules apply accordingly.