The most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system is whether the user requirements were met. User requirements are the specifications and expectations of the users of the system, such as the features, functions, performance, quality, and security of the system. User requirements are usually defined and documented in the early stages of the system acquisition process, such as in the request for proposal (RFP) or the contract. User requirements are also used as the basis for testing and evaluating the system before and after implementation.

Determining whether the user requirements were met can help the IS auditor assess whether the system is fit for purpose and delivers value and benefits to the users and the organization. Determining whether the user requirements were met can also help the IS auditor identify any gaps, issues, or problems with the system that may affect its functionality, usability, or reliability. Determining whether the user requirements were met can also help the IS auditor provide feedback and recommendations for improvement or enhancement of the system.

Stakeholder expectations were identified is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather a prerequisite or input for it. Stakeholder expectations are the needs and wants of the various parties who have an interest or influence in the system, such as users, managers, customers, suppliers, regulators, or auditors. Stakeholder expectations are usually identified and analyzed in the initial stages of the system acquisition process, such as in the feasibility study or the business case. Stakeholder expectations are also used as inputs for defining and prioritizing the user requirements.

Vendor product offered a viable solution is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather an outcome or result of it. Vendor product is the system that is provided by an external supplier or service provider to meet the user requirements. Vendor product offered a viable solution means that the vendor product satisfied or exceeded the user requirements and delivered value and benefits to the users and organization. Vendor product offered a viable solution can be determined by comparing and evaluating the user requirements and the vendor product performance and quality.

Test scenarios reflected operating activities is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather a factor or criterion for it. Test scenarios are sets of conditions or situations that are used to test and verify whether the system meets the user requirements. Test scenarios reflected operating activities means that test scenarios simulated or replicated real-world scenarios that occur during normal operations of business processes or functions that use or depend on the system. Test scenarios reflected operating activities can help ensure that test results are valid, reliable, and relevant.