Maintenance testing is testing performed on a software product after delivery to correct defects or improve performance or other attributes. Maintenance testing can be triggered by various situations, such as modifications to a released software or system, migration of the system data to a replacement system, or retirement of the software or system. Maintenance testing is not executed when there is an update to the maintainability requirements during the development phase, as this is not a maintenance situation but rather a change request that should be handled by the development process. Verified References: [A Study Guide to the ISTQB Foundation Level 2018 Syllabus - Springer], Chapter 2, page 18-19.