Legal Definitions - nonessential mistake

A nonessential mistake is an error or misunderstanding that does not affect the validity of a contract. It is also known as an unessential or collateral mistake. This type of mistake does not relate to the nature of the contents of an agreement, but only to some external circumstance.

For example, if two parties agree to sell a car, but one party mistakenly believes that the car is red when it is actually blue, this would be a nonessential mistake. The mistake does not affect the validity of the contract, as the color of the car is not essential to the agreement.

Another example would be if two parties agree to sell a car, but one party mistakenly believes that the car has 50,000 miles when it actually has 60,000 miles. This would also be a nonessential mistake, as the mistake does not affect the validity of the contract.

In both examples, the mistake is not essential to the agreement and does not affect the validity of the contract. Therefore, it is considered a nonessential mistake.