Software applications are expected to provide reliable performance and error-free functionality in real-world environments. To achieve this goal, software testing is performed during different stages of development to identify and correct defects before release. Even after extensive testing, some issues may remain unnoticed and later appear in the production environment when the software is used by customers. These escaped issues are known as defect leakage. The presence of defect leakage reflects limitations in the testing process and affects the overall quality of the software product.

This research focuses on understanding the reasons behind defect leakage and identifying methods to reduce its occurrence in software projects. The study explains how factors such as incomplete requirements, insufficient test scenarios, weak regression testing, lack of communication, and limited testing time contribute to production defects. The paper also discusses the effect of defect leakage on software maintenance, customer experience, business operations, and project cost.