Which is a common requirement of all parties involved in a contract?

The requirement of an exchange of consideration is fundamental in contract law. Consideration refers to something of value that is exchanged between the parties involved. This could be in the form of money, services, goods, or a promise to do or not do something. The key aspect of consideration is that it represents a mutual exchange, signifying that both parties have something to gain and something to give up, which is essential for the formation of a valid contract.

Without consideration, a contract is generally unenforceable because there is no incentive for either party to uphold their part of the agreement. Each party's promise to perform (or refrain from doing something) serves as the consideration that binds the contract. This is a foundational principle in contract law, ensuring that agreements are not one-sided and that both parties have a stake in the arrangement.

While other factors like mutual agreement on terms or written documentation may be important for clarity and enforceability, they are not universally required for all contracts. Witnesses may be necessary in some cases, such as for wills or real estate transactions, but they are not a requirement in every contract scenario.