What is typically necessary for a legally binding contract?

For a contract to be legally binding, it must have a legal purpose, which means that the agreement must be for a legitimate reason and not for something illegal or against public policy. This is a fundamental aspect of contract law, as any agreement that involves illegal activities or violates the law cannot be enforced.

While notarization, written form, and witness signatures can add layers of formality or serve certain legal functions in specific scenarios, they are not universally necessary for a contract to be valid. In many cases, oral agreements or informal arrangements can be legally binding if they fulfill the essential elements required under contract law, provided that the contract's purpose is legal. Thus, having a lawful objective is the cornerstone of a valid contract, making it the most crucial requirement among the options presented.