To stop a reverse transfer in Odoo 16 from being done for more than the delivered quantity, you can implement an automated action or override the relevant Odoo method to enforce this restriction.

Here’s how you can implement this:

1. Understanding the Requirement

• Reverse Transfer: This process is initiated from the original delivery picking to return goods.
• Delivered Quantity: You need to ensure that the return quantity does not exceed the delivered quantity.

2. Automated Action Approach

You can create an Automated Action that validates the return picking quantity before confirmation.

Steps to Create Automated Action

1. Activate Developer Mode:
   • Go to Settings > Activate Developer Mode.
2. Navigate to Automated Actions:
   • Go to Settings > Technical > Automated Actions.
3. Create a New Automated Action:
   • Model: stock.move
   • Trigger: On Creation & Update
   • Condition: Add a domain to target only reverse transfers:

     [('picking_type_id.code', '=', 'incoming'), ('origin_returned_move_id', '!=', False)]
     

   • Python Code:

     for record in records:
         if record.origin_returned_move_id:
             delivered_qty = record.origin_returned_move_id.quantity_done
             if record.quantity_done > delivered_qty:
                 raise UserError(
                     "You cannot return more than the delivered quantity! Delivered: %s, Trying to Return: %s" %
                     (delivered_qty, record.quantity_done)
                 )
     

3. Server-Side Method Override (Recommended)

If your team is familiar with Odoo development, overriding the button_validate method on the stock.picking model ensures this logic is enforced at the server level.

Steps to Implement

1. Create a Custom Module: If you don’t have one already, create a custom module.
2. Extend the stock.picking Model: Override the button_validate method to add validation for reverse transfers.
   Code Example:

   from odoo import models, api
   from odoo.exceptions import UserError
   
   class StockPicking(models.Model):
       _inherit = 'stock.picking'
   
       @api.model
       def button_validate(self):
           for move in self.move_ids_without_package:
               if move.origin_returned_move_id:
                   delivered_qty = move.origin_returned_move_id.quantity_done
                   if move.quantity_done > delivered_qty:
                       raise UserError(
                           "You cannot return more than the delivered quantity! Delivered: %s, Trying to Return: %s" %
                           (delivered_qty, move.quantity_done)
                       )
           return super(StockPicking, self).button_validate()
   

3. Restart the Server and Upgrade the Module:
   • Restart the Odoo server.
   • Upgrade the module.

   ./odoo-bin -u your_custom_module_name
   

4. Testing

• Create a sales order and confirm delivery.
• Initiate a reverse transfer.
• Try to input a return quantity greater than the delivered quantity.
• The system should block the operation and raise an appropriate error message.

5. Additional Considerations

• Multi-Line Validation: If reverse transfers have multiple lines, ensure the logic applies to all lines.
• Negative Quantities: Check if your setup allows negative stock, as this can also affect the validation.
• Customizable Messaging: You can improve user feedback by including the product name or other relevant details in the error message.

6. Advantages of the Method

• Automated Action: Quick to implement with minimal technical involvement.
• Server-Side Method: More robust and ensures the rule is enforced even if users bypass the UI (e.g., through API).

By implementing one of these approaches, you can effectively prevent your team from returning more items than were delivered, maintaining accurate stock and sales order records. Let me know if you need further clarification or help!