Which of the following is NOT one of the essential elements of a valid contract?

Written documentation is not one of the essential elements of a valid contract. The fundamental requirements for a contract to be valid include consideration, legality of object, and offer and acceptance.

Consideration refers to something of value that is exchanged between the parties involved, which is central to forming an agreement. The legality of the object means that the purpose of the contract must be legal; if a contract involves illegal activities, it cannot be enforced. Offer and acceptance are crucial because they indicate that one party has proposed terms and the other has agreed to them, establishing mutual consent.

While having a written document can be beneficial in supporting the existence and terms of a contract, it is not always required for a contract to be valid. Many contracts can be binding even if they are verbal or implied. Therefore, the absence of written documentation does not invalidate a contract, making it the correct answer to this question.