How Do I Revoke or Cancel a Power of Attorney in Alberta?

This answer covers the law of Alberta.

If you are the donor and still mentally capable, you can cancel an enduring power of attorney in Alberta by revoking it in writing, unless it is an irrevocable one. If the donor is no longer mentally capable, they cannot revoke it.

Revocation is not the only way one ends. Other endings include the attorney renouncing, a court termination order, a trusteeship order for the donor or the attorney, and death. With several or alternate attorneys, these events refer to the last remaining attorney, so one attorney's departure does not end the document while another can act.

Once capacity is lost, any interested person may apply to the Court of King's Bench to terminate it if that would be in the donor's best interests. The Court cannot appoint a substitute attorney, but may direct the applicant to seek a trusteeship order. Telling the attorney and the donor's banks in writing is a sensible practical step, because an attorney who acts after the authority has ended without knowing it has ended is generally not liable. What each bank requires varies, so a lawyer can confirm the steps for your situation.