All About Estates

Difference Between a POA and an SDM

Written by Fatima Husnain, student-at-law at Fasken Martineau DuMoulin LLP

Prior to law school, I worked in a hospital inpatient mental health unit. Many of the patients were unable to make their own health care decisions and relied upon other individuals to make decisions on their behalf. If anyone had asked me at that time what a power of attorney for personal care (“POA”) was, I could not have answered. Almost none of the patients I interacted with had a POA. Instead, the vast majority of individuals relied on a substitute decision maker (“SDM”), typically a family member who was chosen on their behalf, to make their health care decisions. In today’s post I will explore the difference between a POA and an SDM.

Section 20 of the Health Care Consent Act (“Act”), sets out the hierarchy of individuals that may receive decision making power when a person is incapable:

  1. A guardian of the person, if the guardian has authority to give or refuse consent to the treatment;
  2. An attorney for personal care, if the power of attorney confers authority to give or refuse consent to the treatment;
  3. A representative appointed by the Consent and Capacity Board;
  4. A spouse or partner;
  5. A child or parent, or a children’s aid society or other person who is lawfully entitled to give or refuse consent to the treatment in the place of the parent;
  6. A parent who has only a right of access;
  7. A brother or sister; and
  8. Any other relative.

The Act states that the SDM is “a person who is authorized under section 20 [of the Act] to give or refuse treatment on behalf of a person who is incapable with respect to the treatment”. The SDM must be willing and able to take on this role (they must also be capable and at least 16 years old). For people that do not have a guardian or a POA, the decision maker will likely be a family member. The Act will govern to determine which family member will take on this role without input from the incapable person.

Both a POA and an SDM are able to make similar decisions for the incapable person. Both are able to provide consent for treatment, admission into a health care facility and personal assistance service. Personal assistance services include decisions surrounding assistance with hygiene, eating, drinking and other routine activities. However, with a POA, there is more autonomy to determine exactly what decisions the decision maker is able to make.

The SDM system is important as not all individuals will have a formally appointed legal POA. However, if an individual wants to choose the person who will make health decisions on their behalf, it is recommended that he or she create a POA. A POA must be determined prior to a person being deemed incapable. This written document allows the individual to retain some autonomy. A POA can be almost anyone; for example, a person can appoint his or her best friend, or someone lower on the hierarchy provided by the Act. The individual has freedom to choose whoever they want as a decision maker if they subsequently become incapable.

Another benefit to having a POA arises when there are multiple people that qualify as an SDM. The Act dictates that multiple equally ranked individuals can be SDM’s and if they do not agree, the Public Guardian and Trustee will step in to make a decision instead. Having a POA will avoid situations such as this from occurring and will ensure that there is only one decision maker.

Both an SDM and POA are entitled to enough information about the incapable person and their treatment plan in order to make an informed decision. The SDM must then comply with decision making rules set out in the Act. The SDM must also consider any wishes the incapable person made while they were capable, their values and beliefs, the risks and rewards of treatment and if there are any other more beneficial treatment options. For a POA, similar rules regarding decision making apply, however the incapable person has more ability to write out their wishes and authorize the individual to make specific decisions about their personal care.

Overall, it is preferable to have a POA for a number of reasons. First, it gives an individual the ability to select a specific person to become a decision maker; and second, creating a POA ensures that an individual’s wishes are outlined in writing and are subsequently respected. Looking back at my experiences working at the hospital, I definitely know that many people had wished they had set up a POA prior to becoming incapable and retained some autonomy in a situation in which they otherwise have minimal autonomy.

About Emily Hubling
Emily Hubling is a partner in the Trusts, Wills, Estates and Charities group at Fasken. Emily has experience in advising estate trustees in administering a range of complex estate matters, including intestacies, cross-border matters, and contested estates. Working closely with clients’ advisors, Emily prepares Wills, Powers of Attorney, and Trusts to assist clients in fulfilling their unique estate-planning objectives.


  1. Glenn Robitaille

    January 7, 2021 - 1:25 pm

    I was searching for a quick summary to support a conversation with a family around the differences between and SDM and POA for Personal Care and happened upon this. Thank you for this very well-written and succinct summary. Sending it on saved me a whole lot of discussion.

    I should mention that in Ontario, if any family member contests a DNR order, medical staff will resuscitate. Legislation around POA’s is less precise than around SDM’s, and PG&T’s don’t like to make treatment decisions. I work in Ethics in an Ontario Specialty Mental Health Hospital.

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