Mutual Misunderstanding in Contract

Abstract

It is accepted throughout the common law that agreements founded on a mutual misunderstanding are void ab initio. It follows from this that unenforcement is necessary and inevitable; indeed, there is simply no contract to enforce. Curiously, however, in cases involving mutual misunderstanding the parties themselves usually believe and behave as if they have settled upon a knowable and enforceable agreement from the outset. It is typically only sometime later that the mutual misunderstanding between the parties comes to light. In this article I question the wisdom of the widely accepted common law rule surrounding mutual misunderstanding. I present and defend an alternative legal rule that significantly improves upon the efficiency of the results in cases involving mutual misunderstanding. The rule I propose would allow each party to an agreement founded on mutual misunderstanding to have the option to enforce his or her reasonable understanding of the agreement vis-a-vis the other party. This rule can be shown to preserve the reasonable expectations of the parties, promote reliance on promises, and provide implicit insurance against the risk that a mutual misunderstanding will interfere with the realization of expected contractual surplus.