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The Prudent Investor Rule for Trustees Under Ontario Law

See what Ontario's Trustee Act requires when a trustee invests trust money, when a loss can be blamed on the trustee, and what protections apply.

Wills & Estates4 min readTSLBy the Treadstone Law Team · OntarioUpdated November 6, 2026
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Key takeaways
  • A trustee investing trust property must use the care, skill, diligence and judgment of a prudent investor.
  • A trustee is not liable for an investment loss if the conduct that led to it followed a plan or strategy a prudent investor could adopt.
  • The terms of the trust can limit what the Act's investment powers allow.

If you are a trustee in Ontario and you hold investments for others, you may worry about what happens if the market falls. The law does not expect a trustee to guarantee returns, but it does expect a careful process.

This article explains the main investment rules in Ontario's Trustee Act and the protections that can apply if something goes wrong.

The standard: a prudent investor

Under the Trustee Act, in investing trust property, a trustee must use the care, skill, diligence and judgment of a prudent investor. In plain words, the standard asks what a careful, sensible investor would do when managing money that belongs to other people.

What a careful process includes

When planning investments, a trustee must consider the criteria listed in the Act and must diversify to an appropriate extent. A trustee may also obtain investment advice. A trustee may delegate investment functions to an agent.

The trust document comes first

The Act's investment powers do not authorize or require a trustee to act inconsistently with the terms of the trust. A will or trust deed might limit the kinds of investments you may hold, or it might require you to keep a particular asset. Read the document before you rely on the general rules.

When a trustee is blamed for a loss

A trustee is not liable for an investment loss if the conduct that led to the loss followed an investment plan or strategy that a prudent investor could adopt. Whether a particular plan meets that description depends on the facts, so it is worth confirming with a lawyer.

Separately, a court may relieve a trustee wholly or partly from personal liability for a breach of trust if the trustee acted honestly and reasonably and ought fairly to be excused. This relief does not apply to losses from investing trust property. For those losses, the trustee relies on the plan-or-strategy protection.

QuestionWhere the answer comes from
Did you invest with a prudent investor's care and judgment?Trustee Act s. 27(1)
Did your conduct follow a plan a prudent investor could adopt?Trustee Act s. 28
Can a court excuse a trustee who acted honestly and reasonably?Trustee Act s. 35(1), but not for investment losses

What a beneficiary can do if they are unhappy with a trustee's investment decisions depends on the facts, so it is worth confirming with a lawyer. For estate trustees, the Superior Court of Justice may remove them on any ground on which it could remove any other trustee, and appoint someone else in their place. The general limitation period is two years from the day a claim was discovered, with exceptions, so timing matters.

What to do next

If you are unsure how to proceed, a trustee may apply to the Superior Court of Justice, without starting an action, for the court's opinion, advice or direction on managing trust property. A trustee may also pay a trust expense personally and recover it from the trust property, although the court may later disallow it.

Frequently asked questions

Does the prudent investor rule mean a trustee can never lose money?

No. A trustee is not liable for an investment loss if the conduct that led to it followed an investment plan or strategy that a prudent investor could adopt. The focus is on the process and the plan.

Can a trustee hire an investment manager?

Yes. A trustee may obtain investment advice and may delegate investment functions to an agent under the Trustee Act. A lawyer can explain how to set up and document the arrangement.

Can a court excuse a trustee who made an honest mistake with investments?

A court can relieve a trustee of personal liability for a breach of trust if the trustee acted honestly and reasonably. That relief does not apply to investment losses, which are dealt with under the plan-or-strategy protection.

What if the will says to invest in a certain way?

The Act's investment powers do not authorize or require a trustee to act inconsistently with the terms of the trust. If the terms are unclear or no longer workable, a trustee may ask the court for directions.

Sources

Links go to official government, court and regulator pages. The law changes — confirm you are reading the current version.

This article is general information, not legal advice. Reading it does not create a lawyer-client relationship. Ontario laws, tax rates, and government programs change, and how the law applies depends on your specific facts. For advice about your situation, speak with a licensed Ontario lawyer. Treadstone Law is licensed by the Law Society of Ontario — reach us at 1-844-900-1070 or start a file online.

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