ABSENSE OF MUTUAL ASSENT:
If only one of the parties is mistaken about facts relating to the agreement, the mistake will not prevent formation of a contract. However, if the nonmistaken party knew or had reason to know of the mistake, the contract is voidable by the mistaken party.
Contracts with errors, such as computation mistakes, may be canceled in equity, assuming that the nonmistaken party has not relied on the contract. There is also modern authority indicating that a unilateral mistake that is so extreme that it outweighs the other party's expectations under the agreement will be a ground for cancellation of the contract.
An error in judgment by one of the parties as to the value or quality of the work done or goods contracted for will not prevent formation of a contract even if the nonmistaken party knows or has reason to know of the mistake made by the other party.