A policy provision usually inserted into the preamble to a group of exclusions in a property insurance policy that is designed to combat the misapplication of the concurrent cause doctrine from tort law to a first-party property policy.

(1) A tort doctrine that imposes joint liability on two or more parties if their negligence combines to produce the same loss. (2) In property insurance, this term refers to a situation where there is a mixture of covered and uncovered perils acting together (either in sequence or simultaneously) to produce the same property damage. In the early 1980s, lower courts in California misapplied tort concepts to the interpretation of first-party property policies and held that, in "concurrent causation" claims, the property insurer is liable so long as one of the causes is covered by the policy. As a result, these courts refused to enforce flood or earthquake exclusions if there was an unexcluded factor contributing to the loss, such as zoning decisions or the negligence of a contractor. In response, insurers added so-called anti-concurrent causation (ACC) language to standard homeowners, commercial property, and other first-party property policy forms to combat this line of thinking. (3) In liability insurance, this term is occasionally used to refer to a situation where there are two or more causes of action asserted in the complaint against the insured, any one of which would be sufficient by itself to hold the insured liable, but some of the causes of action are covered and some are not. In that situation, the liability insurer must defend the entire complaint.