Maybe I didn’t explain myself, I don’t expect the receipt to change but I would like the “received quantity” on the purchase to update.

The business case I try to explain is this:

• I ordered 13 units of product A using a Purchase order.

• I received the 13 units

• PO quantity: 13 units
• "Shipment one" quantity: 13 units
• PO received quantity: 13 units  

•  After the inbound process I realize the 5 units were broken and I return them to the vendor reversing "shipment one":

• PO quantity: 13 units
• "Shipment one" quantity: 13 units  
• Return shipment quantity: 5 units  
• PO received quantity: 13 units --> I expected that after the reverse/return this quantity were 8.  

·        The vendor tells me that he´s not got stock so we agree to invoice only 8 units and close the purchase order. I create the invoice and the system proposes 13 units. On the purchase order we cannot see any trace of what happened (the received quantity hasn´t changed) and the return shipment is no accessible or visible from the purchase order. All these factors will trigger  an incorrect invoice.  

Is there anything we can do to solve this issue? Maybe there is another way to do it and I don’t know how this process works in Odoo.

It won't work this way in Odoo without customization - Odoo is working exactly the way it is designed to work out of the box.

Since 13 units came in, there will be a record that 13 came in.

When you reverse the shipment and select 5, there will be another record that 5 went back.  

The fact that 13 came in hasn't changed, which is why it won't update the Receipt - Odoo will just record the reverse as a second record that reduces the net quantity in stock to 8 units.

What was the reason for 13 units being received?  If this was a mistake, you may want a record of the mistake so you can keep track of users who need additional training.  If you don't, you can customize Odoo to allow you to 'reset' the Receipt as if nothing happened (but then you lose any record of the mistake) and proceed to receive 8.

Ray, I agree with Nacho's point of view in the sense that it would make the flow more intuitive.

So, as long as you have not entered the supplier invoice, you should be able to return with reference to that PO for the PO lines and quantities not yet invoiced, and the system should reduce the quantity to invoice. Quantity received - quantity returned = quantity to invoice. Because you, as a customer, do not acknowledge these quantities to be included in the supplier invoice.

In this same sense, if the supplier uses Odoo, he should be able to return the quantities delivered, provided that they have not been invoiced yet, reducing the quantity to invoice.

If the customer invoice have been posted and sent at the supplier side, then I agree that it is the obligation of the customer to accept the invoice. The initiating supplier invoice should then be posted with the original quantity received. Then the return should be part of a separate process, with separate refund invoice.

So, that is, adjustments in the quantity to invoice resulting from disputes between the supplier and customer, before invoices have been generated, should become part of the same transaction. But once the invoice has been sent, a new transaction flow must be initiated.