Hi,

In Odoo, warehouse documents such as Delivery Orders, Receipts, and Internal Transfers cannot be directly cancelled once the transfer is marked as Completed (or Done), as the system locks these records to maintain inventory accuracy and traceability. If you need to undo a completed transfer, the proper method is to use the Reverse Transfer option. This action creates a new warehouse transfer that moves the products back to their original location, effectively reversing the stock movement. This ensures that inventory levels remain consistent and that all changes are properly logged. Cancelling a done transfer directly is not allowed by default to prevent inconsistencies in stock and accounting, so using Reverse Transfer is the recommended and traceable solution.

Hope it helps.