What does it mean to be an additional insured and how does that affect a coverage dispute in Ontario?

Being named an additional insured means you get coverage under someone else's insurance policy - typically added by endorsement - without being the original policyholder who bought it. This comes up often in commercial and construction settings: a landlord added to a tenant's liability policy, or a general contractor added to a subcontractor's policy, so that a claim arising from the other party's operations is covered under that existing policy rather than requiring you to rely solely on your own insurance.

The scope of what's actually covered depends entirely on the specific endorsement wording - some additional insured endorsements are broad, covering essentially any liability arising from the named insured's work, while others are narrower and limited to specific operations, locations, or time periods. In a coverage dispute, the first question is always what the endorsement actually says, since "being an additional insured" isn't a single standard status with fixed protection - it varies policy to policy. If a claim arises and you believe you should be covered as an additional insured, get the actual endorsement wording early, since a denial is often really a dispute about how narrowly or broadly that specific language should be read.