Defined term
Anti-concurrent causation
An anti-concurrent causation clause is a policy provision excluding coverage if any portion of the loss was caused by an excluded peril — even where a covered peril also contributed.
ACC clauses are most often litigated after hurricanes, where wind damage (typically covered) and flood damage (typically excluded) occur to the same property. The ACC clause attempts to exclude coverage if any part of the loss was caused by the excluded peril, regardless of whether covered perils also contributed.
Courts split on enforceability. Some give full effect to ACC clauses; others apply concurrent-causation doctrine and find coverage where a covered cause was a substantial factor. The practical battle is over which water caused which damage, requiring engineers, hydrologists, and detailed loss-by-loss documentation.