An attempted contract that is made for an illegal purpose or that is against public policy cannot be enforced by either party and is void. In contrast, a contract that is made by a minor (usually under age 18), or that is based on a mutual mistake, or that was made on the basis of a fraudulent misrepresentation by one party, is voidable and may be rejected by a party who was at a disadvantage when the contract was made. A voidable contract may also be ratified and accepted by such a party—after a child reaches the age of majority (usually 18), or the parties become aware of their mutual mistake, or a party learns of the other party’s misrepresentation and proceeds with performance of the contract.

In Wisconsin, contracts made for illegal purposes or against public policy are void and unenforceable by law. This means that no party can seek legal remedy to enforce such a contract. On the other hand, contracts that involve minors (typically under the age of 18), are based on mutual mistakes, or are formed due to fraudulent misrepresentation by one of the parties, are considered voidable. Voidable contracts can be rejected or affirmed by the disadvantaged party. For instance, a minor has the right to disaffirm a contract before reaching the age of majority, which is 18 in Wisconsin, and for a reasonable time after reaching it. However, they may also choose to ratify the contract upon reaching the age of majority. Similarly, parties to a contract based on a mutual mistake or fraudulent misrepresentation can either rescind the contract upon discovering the issue or ratify it by continuing with the contract's performance.