Burlington Insurance Company refused to cover injuries to NYC Transit Authority (the additional insured) under a policy issued to Breaking Solutions Inc. (the named insured). The New York Court of Appeals ruled that an additional insured endorsement only covers injuries that are proximately caused by the named insured's negligence, not injuries caused solely by the additional insured's own negligence. This means you cannot use your subcontractor's insurance to cover your own mistakes—the subcontractor must actually be at fault for the injury.
Additional insured coverage requires proximate causation, not just a causal link. Your client cannot collect under your policy if they caused the injury themselves.
Review your insurance endorsements carefully. Broad language like 'caused in whole or in part' does not mean unlimited coverage for the additional insured.