Common Mistake

What is Common Mistake in Contract Law?

Quick Definition

Common mistake occurs when both parties to a contract share the same fundamental error about a fact that is essential to the agreement. If the mistake is serious enough, it may render the contract void. The mistake must go to the root of the contract, not just a minor detail.

In Context

Common mistake typically arises where both parties assume something exists or is true, but it is not. For example, if both buyer and seller believe a specific ship exists when it has already been destroyed, the contract may be void due to a shared mistaken assumption. In Bell v Lever Brothers, the court held that a contract is not automatically void just because both parties were mistaken; the mistake must make performance essentially different from what was agreed. This shows that courts apply a high threshold before setting aside contracts on this ground. In exams, the key issue is whether the mistake fundamentally undermines the identity or existence of the subject matter.

See Also

• Mutual Mistake

• Frustration of Contract

• Void Contracts

Learn More

Explore our Contract Law Notes for clearer case breakdowns, exam-focused structures, and practical guidance on spotting when shared error truly invalidates a contract.