Consider the case:

• client enters website,

• adds to cart 20 pieces of Product_A  +  40 pieces of Product_B,

• pays online.

Now, SO is confirmed, procurements created. All is fine with Product_A.
For Product_B, only 1 piece is in stock + all suppliers are out of stock too.

Situation where procurement cannot be fulfilled, but payment already done.
Similar case - where procurement could be fulfilled only partially.

What to do in this case?    -- especially with procurement and stock moves!

1. With accounting (invoice, payment):

2. 1.  Invoice
      

   2. 1. Should a complete invoice be created and then another refund invoice will compensate for 39 pieces (or for the whole SO line, if client wants to cancel the whole line)?

      2. Or a draft invoice should be corrected to reflect the real situation (40 => 1 or line removed at all)?

   3. Payment:

   4. 1. What to do with the payment (voucher) in each of these cases? How do we reflect the fact of payment of 40 pieces and then pay the client back? AFAIK, there is no such thing as refund payment. Of course, excess amount could be "Kept open" as credit, but what to do with a random client who won't come back again?

3. With stock:

4. 1. Procurement has its quantity fixed once confirmed, so stock will still wait for 40 pieces.
      We could pretend that we've actually received 40 pieces, would receive them in Odoo and would then make a "Reverse Transfer" from Delivery Picking of those excess 39 pieces. But that would look as if the client has received all of those 40 pieces and then returned 39
      

What would be the right way to register in the system that we only received 1 piece in fact?

And how to make procurement aware of the fact that we no longer need 40 pieces, but 1 or not at all?