We are not sure yet if the company charges the client for the service for stock keeping
No, we don't charge it as aditional service, the service is "include" in the sales price....
I am a bit concerned about the idea of delaying goods issue for the sales transaction
In our company we have a "rule": No item is out of plant if there's not an legal invoice.... so the solutions should consider that
The proforma solution - as you pointed out, it really depends on what the customer will agree on. He most probably wishes to receive a legal invoice in the current period and will send payment with reference to the proforma number.
They ask for legal invoice. In Fact, in Mexico the "proforma" invoice is not very common.
Transportation cost in case we use a single delivery in the process - unless the company uses a very basic calculation for these costs, which can be reliably predicted before shipment creation and entered manually in the documents, the only possible way I can think of unfortunately is a separate payment only for the transportation charges.
We use LES for transportation cost. We create a later invoice to customer if the shipment should be paid by them. (We pay to freight vendor, and then we invoice the freight to customer if it should be charged to them...)
Thanks for your great effort