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What Is Duty to Defend?
A duty to defend is a contractual obligation to defend another party against claims, paying their legal costs as soon as an allegation is made and before fault is decided. It is broader than a duty to indemnify, which applies only once liability is established.
This is a critical insurance trap for design professionals. A professional liability (E&O) policy defends you, the named insured, not a third party you have promised to defend, and there is no additional insured mechanism on E&O. Agreeing to defend a client usually means paying their legal bills yourself. See our engineering contract review guide.
Questions about Duty to Defend?
Our Ontario brokers can explain how it applies to your policy.
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Reviewed by Roughley Insurance Brokers Ltd. — licensed Ontario insurance brokers since 1945. Last updated June 21, 2026. ← Back to the glossary