The present study examined the impact of Lean service methodology and work standardization on the customer disengagement process in a Peruvian based company in the banking and finance sector. Data was collected before and after implementation to identify issues and design solutions based on 5S and work standardization. The results highlighted the significant impact of these methodologies on the customer disengagement process. By conducting root cause analysis using the problem tree tool, issues such as low standardization in creating letters and information request emails, delays in identifying responses to customers and relationship managers, disorganized databases storing historical communications, lack of standardization in comments for manager approval, and delays in confirming information receptions were identified. Implementing engineering solutions based on the mentioned methodologies, such as mass creation and standardization of information requests, setting up an automated flow for request reception, organizing and standardizing information databases, and eliminating unnecessary data within these, led to an 80% improvement in the disengagement process efficiency. The application of the 5S methodology and work standardization proved effective within the company. It allowed for the identification and addressing of root causes, resulting in time improvements such as a 94% reduction in registration and query time in the customer response reception database, a 66% reduction in time for sending requests to managers, and a 91% reduction in registration and query time in the manager's database. These contributed to reducing operational recurrence costs by over 70,000 Peruvian nuevos soles (PEN) per year. These findings underscore the importance of implementing Lean Service tools in the banking and finance sector to achieve greater operational efficiency and service quality for customers and stakeholders.