Mistake (contract Law) - Mutual Mistake

Mutual Mistake

A mutual mistake occurs when the parties to a contract are both mistaken about the same material fact within their contract. They are at cross-purposes. There is a meeting of the minds, but the parties are mistaken. Hence the contract is voidable. Collateral mistakes will not afford the right of rescission. A collateral mistake is one that 'does not go to the heart' of the contract. For a mutual mistake to be void, then the item the parties are mistaken about must be material (emphasis added). When there is a material mistake about a material aspect of the contract, the essential purpose of the contract, there is the question of the assumption of the risk. Who has the risk contractually? Who bears the risk by custom? Restatement (Second) Contracts Sec. 154 deals with this scenario.

This is easily confused with mutual assent cases such as Raffles v Wichelhaus.

In Raffles, there was an agreement to ship goods on a vessel named Peerless, but each party was referring to a different vessel. Therefore, each party had a different understanding that they did not communicate about when the goods would be shipped.

In this case, both parties believed there was a "meeting of the minds," but discovered that they were each mistaken about the other party's different meaning. This represents not a mutual mistake but a failure of mutual assent. In this situation, no contract has been formed, since mutual assent is required in the formation stage of contract. Restatement (Second) Contracts Sec. 20 deals with this scenario.