The final element of a valid contract is legality. This means that if a contract requires one of the parties to perform an illegal action, it would be declared void. If Liz offers to pay Ben $300 to break into her neighbor’s house, then refuses to pay him after he does, Ben cannot sue Liz for breaching her contract. Similarly, if either party enters into a contract illegally, the contract is generally unenforceable. For example, this would apply if someone formed a contract with an unlicensed professional when the law requires someone in that profession to have a license.