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 Iowa, contracts made for illegal purposes or against public policy are considered void and unenforceable. This aligns with general contract law principles that prohibit the enforcement of agreements that involve illegal acts or that significantly contravene societal standards. On the other hand, contracts that involve minors, are based on mutual mistakes, or are entered into because of fraudulent misrepresentation are categorized as voidable. This means that the disadvantaged party has the option to either reject or ratify the contract. In the case of minors, once they reach the age of majority, which is typically 18 years old, they can choose to affirm or disaffirm the contract. Similarly, parties who enter into a contract under a mutual mistake or due to one party's fraudulent misrepresentation can decide to continue with the contract upon discovering the issue or may choose to void it. It's important to note that specific circumstances and additional state statutes may further define and regulate these principles.