Mergers and acquisitions offer strategic growth opportunities, but integrating newly acquired systems poses significant challenges—especially in financial services. This article explores the complexities of system incompatibility and data migration, highlighting how legacy technologies, manual processes, and security vulnerabilities can derail integration efforts. Drawing on experience from four M&A programs, it outlines key risks such as incompatible software, user-defined applications, and AI-related disruptions. Effective planning, early risk identification, and robust data management are essential to avoid delays, cost overruns, and operational breakdowns