Like piling hay bales onto the same wagon, stacking means adding one insurance limit on top of another instead of stopping with a single policy limit. In insurance and legal use, it usually means combining coverage available from multiple vehicles, multiple policies, or multiple coverages to increase the total amount payable for a loss. The issue comes up most often with uninsured motorist coverage, underinsured motorist coverage, medical payments coverage, and sometimes liability coverage.

Whether stacking is allowed depends on the policy language and state law. Some policies expressly permit it. Others contain anti-stacking clauses that try to limit recovery to one vehicle's or one policy's highest limit. In Vermont, auto insurance is governed in part by 8 V.S.A. § 4203 (2024), which requires UM/UIM coverage, but that statute does not create a blanket right to stack every available limit. The answer usually turns on the exact contract wording.

For an injury claim, stacking can change the value of the case by tens of thousands of dollars. If damages exceed one available limit, stacked coverage may fill more of the gap after a crash, especially where medical bills and lost wages are high.

It also affects settlement strategy. An insurer may cite anti-stacking language to cap payment, while a claimant may argue that separate premiums, separate vehicles, or ambiguous wording allow additional recovery under the insurance policy.