Hi,

Migrating from Odoo 15 Enterprise to Odoo 18 without access to the original vendor’s code or Odoo.sh repository is indeed complex, especially since the enterprise version requires a valid license and code compatibility. Of the three options you’ve outlined, each has trade-offs depending on your priorities, cost, accuracy, and time.

Maintaining a perpetual subscription is the easiest way to preserve data integrity and ensure legal access to the codebase, but if the company refuses to pay, it’s not a viable path. The schema-to-schema migration (option 2) is the most technically accurate approach since it preserves relationships and dependencies across tables, but it demands deep database knowledge and time to validate all models. It’s best suited if data consistency and accounting traceability are top priorities.

The manual loading option (option 3) is more practical if you can tolerate some data loss in non-critical areas and rely mainly on high-level historical data (e.g., balances, inventory valuations, or sales summaries). Using RPA scripts or import templates could make this feasible within your 3–4 month timeframe, though care is needed with computed fields and transaction order.

In short, if your goal is accuracy and continuity, go with schema mapping and scripts; if you prioritize speed and simplicity, opt for manual imports with automation support. A hybrid approach, automating imports for master data and scripting key financial and stock movements,often offers the best balance for migrations like this.

Hope it helps

You have several options:

1 - IDEAL / NO WORK AT ALL

It may be possible to keep a single read only license to your old system

• Pros - easy to look things up, nothing new to learn
• Cons - it is another system, so now things are in two places

2 - QUICKEST / EASIEST

Import Excel sheets of the relevant information into Odoo Spreadsheets via the Documents App

• Pros - get access to what you need without much work to import
• Cons - harder to search for things, not integrated well

3 - MORE WORK

Create a Studio App and import tables of CSV data

• Pros - can use Odoo filtering and search, form and list and kanban views, can link to Customers via Smart buttons
• Cons - takes more time

4 - EVEN MORE WORK

Import Monthly Trial Balances

• Pros - you can run year on year comparisons
• Cons - takes even more time

5 - THE MOST WORK

Import Transactions

• Pros - works as if you were using Odoo the whole time
• Cons - VERY VERY VERY time consuming, needs scripts, very advanced knowledge required, may not have a good return on investment