Anti-stacking provisions are intended to avoid the application of multiple sets of deductibles or multiple sets of limits to a single loss event. They are sometimes included in insurance policies covering exposures that may occur over long periods, triggering coverage under multiple policies. They stipulate that, in such an event, only one policy limit or one deductible (rather than the limit or deductible under each policy) applies to the occurrence.

Anti-stacking provisions (or stacking provisions) may be addressed in a state's motor vehicle insurance statutes with respect to uninsured motorists (UM)/underinsured motorists (UIM) coverage. These provisions vary widely from one state to another; and where a state's legislators or court system has addressed the issue, the UM/UIM endorsements in the state are often modified to reflect the state's stance on the issue.

"Stacking" is the aggregation of multiple insurance coverages or limits to cover a single loss. Attempts to "stack" coverage can be based on a theory that a single policy provides more than a single limit of coverage applicable to the claim. This is called intrapolicy stacking.

The application of two or more policies' limits to a single occurrence or claim. This is common with product liability, construction defect, and pollution claims in which the occurrence has transpired over numerous years, and it is difficult to ascertain which policy provides coverage. It can also occur under auto liability or uninsured motorists (UM)/underinsured motorists (UIM) coverage in the business auto policy (BAP) or the personal auto policy (PAP) when two or more vehicle limits can be stacked to apply to a single occurrence.