User acceptance testing (UAT) is a process that should be done by the business analyst after the software developers have delivered a completed solution and the quality assurance team has passed it. User acceptance testing is a process of verifying that the solution meets the requirements and expectations of the end users and delivers value to them. User acceptance testing involves preparing test cases, scenarios, or scripts based on the acceptance criteria, executing them with representative users or stakeholders, collecting feedback, identifying defects or issues, and obtaining sign-off or approval for deployment. User acceptance testing can help to ensure that the solution is fit for use, suitable for purpose, and aligned with business objectives. Evaluating the solution against the project charter is not necessary at this stage, as it does not involve testing or validation by the end users or stakeholders. Evaluating the solution with the sponsor(s) is not sufficient at this stage, as it does not capture the perspective of all relevant users or stakeholders who will use or benefit from the solution. Conducting performance testing is not relevant at this stage, as it is usually done by the quality assurance team before delivering the solution to ensure that it meets the non-functional requirements such as speed, reliability, scalability, etc. References: PMI Professional in Business Analysis (PMI-PBA)® Examination Content Outline1, page 14; Business Analysis for Practitioners: A Practice Guide2, page 80.