When requirements express contractual obligations, acceptance criteria are necessary. These criteria ensure that the requirements meet the agreed-upon standards and conditions set forth in the contract. They provide a clear and measurable way to determine whether the requirements have been met satisfactorily. Acceptance criteria are used to evaluate whether the solution fulfills the contract's terms, and they form the basis for the formal acceptance of the project's deliverables. Reference: The BABOK Guide discusses the importance of acceptance criteria, especially when dealing with requirements that have contractual implications, ensuring that the deliverables meet the predefined standards and are accepted by the stakeholders1.