A contract is sometimes void or voidable because one or both parties made a mistake when entering the contract. With regard to types of mistakes and whether they affect a contracts validity, it generally is correct to say thatthe incontestability provision in life insurance policies prohibits a contest of the policy on the grounds of a mistake of factmistakes of law can render a contract void or voidablea unilateral mistake occurs when both parties to a contract make the same mistakea contract is void when the parties to the contract make a common mistake as to the identity or existence of the subject matter of the contract