and it can happen that in an invoice needs to be modified at the last moment to change the courier.
Fiorenzo,
Why your company needs to modify the courier after completion of the billing document (VF02) or during the creation of billing document (VF01)?
Some business scenarios:
1. Some companies have fixed couriers, during order creation, you input that courier company, in the partner section or its automatically picked up from the customer master. This information then flows to the delivery and finally to the billing document.
2. Sometimes courier is changed after order creation. Then user has the option to go into the delivery and change the courier in tab partners. This updated courier will flow from delivery to the billing document.
Here the sales order and delivery will have different courier details.
As discussed above and in the OSS note, billing document takes the information from its preceding documents. Or else, there would be data mismatch and inaccuracy, that might make reporting etc. much less effective.
TW