Which of the following is NOT a required element for a valid contract?

In the context of contract law, a valid contract must include several essential elements, but written documentation is not always required for a contract to be considered valid. While having a written contract is advisable for clarity and enforcement, many contracts can be legally binding if they are made verbally and fulfill the other necessary conditions.

The main elements required for a valid contract include competent parties, meaning that all parties involved must have the legal capacity to enter into a contract, acceptance, which signifies that all parties agree to the terms of the contract, and legality of purpose, indicating that the contract's purpose must be lawful. Therefore, since written documentation is not a strict requirement in every case, it is the correct choice as the answer to the question posed.