impracticability
Impracticability is a defense in contract law that will excuse performance when an event occurs after the formation of the contract that renders performance of the contract excessively difficult or expensive. The event must not be the fault of the party offering the defense, and the non-occurrence of the event must have been a basic assumption of the contract.
Impracticability is not to be confused with the similar doctrine of impossibility in which an event renders a contract impossible to perform. A contract that is voided on grounds of impracticability may still be possible to perform, but doing so would be so difficult or expensive that performance is unrealistic.
For example, A is selling a product to B. The parties contract for A to ship the product to B. After the contract has been formed, the only port within 1000 miles of B closes. Both parties had assumed that the product would be shipped through the now-closed port. Although the contract could still be performed, the port closure would cause a substantial increase in shipping costs, which neither party had anticipated. As a result, A will likely be able to get out of performance on the grounds of impracticability.
The doctrine of impracticability is recognized both under the common law and the Uniform Commercial Code. See: U.C.C. § 2-615.
[Last reviewed in March of 2026 by the Wex Definitions Team]
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