Migrating a Large Odoo 11 Installation to Odoo 18 for a UK Client

Summary

ERPixel completed a complex upgrade project for a UK-based company that had been operating on Odoo 11 since the first day of its release. Over the years the system became extremely heavy due to extensive customizations, especially in Accounting and BI reporting.

The client relied on Odoo as the core ERP for more than 100 users across several legal entities. The system supported sales operations, procurement, inventory, manufacturing, finance, and employee management.

The migration required full code porting, repeated data migrations, and adaptation of business processes while the system remained live and continued to evolve.

The project lasted 7 months and involved a 20-person team including analysts, developers, QA specialists, and key users.

This experience is relevant for companies running outdated Odoo versions with heavy customizations, where a standard upgrade is not sufficient and a controlled migration strategy is required.

Before

The client had been operating on Odoo 11 for many years. During that time the system accumulated a large amount of custom code and became increasingly difficult to maintain.

The most critical issue was performance. Many financial and analytical calculations were so heavy that they could not run during working hours. These processes had to be scheduled at night when fewer users were connected to the system.

Operational risks were growing:

• complex customizations in Accounting and BI reporting
• increasing maintenance effort for the development team
• instability during peak workload
• limitations of an unsupported Odoo version
• difficulty introducing new features

At the same time the company continued to grow. New data appeared daily, processes changed, and new functionality was required.

This made the upgrade particularly challenging: the team had to migrate the system while the business was still actively using it.

After

After the migration to Odoo 18, the client received a modern ERP platform capable of supporting further growth.

Key improvements included:

• significantly improved system performance
• elimination of architectural limitations from the legacy version
• access to modern Odoo features and updated modules
• simplified maintenance of custom functionality
• improved reliability and scalability

The new environment allows the company to process operational workloads without relying on heavy overnight calculations.

More importantly, the business is no longer constrained by legacy architecture. The ERP system now provides a stable foundation for future development, integrations, and analytical capabilities.

Implementation Details

Modules Implemented

• CRM
• Sales
• Purchase
• Inventory
• Manufacturing
• Accounting
• Employees

Payroll and Marketing modules were not used in the client’s architecture.

Integrations

The system includes multiple connectors to external services and analytical systems, which are used for operational integrations and BI reporting.

Technical Challenges

This migration required solving several complex engineering problems:

1. Migration from an unsupported legacy version
The client operated on Odoo 11 for many years. Standard upgrade paths were not applicable due to the volume of changes in the system.

2. Large volume of custom modules
Most customizations were related to Accounting logic and BI reporting. These modules had to be carefully analyzed, rewritten, and adapted to the architecture of Odoo 18.

3. Continuous business operations during migration
The system remained active throughout the project.

While the upgrade was in progress:

• new transactions were created daily
• business processes continued to evolve
• new data appeared in the system

This required multiple cycles of code migration and data migration.

4. Repeated synchronization of evolving data
Every migration iteration required updating the database snapshot while preserving new operational data generated by the business.

5. Performance optimization
The legacy system relied on heavy background calculations. During the upgrade the team redesigned parts of the logic to take advantage of improvements in the modern Odoo architecture.

Contact

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