Prices are often linked to monthly indexes of commodities from which the invoiced product is made of, e.g. monthly average crude iol WTI. Thus, final product price is only known after the end of a calender month. However, invoices must be raised with every shipment, often due to high amounts invoiced for financial reasons. Thus, invoices with provisional prices (e.g. average commodity price of the previous month) are issued. Same applies for trades in commodities themselves.
Issue
Usually such provisional invoices are only feasible in situations with 0 VAT shown in the invoice due to Article 203 VAT System Directive (cp. point "Final invoice after provisional invoice").
Solution
Invoice needs a separate description as "provisional inoice", otherwise the same fields as any similar commercial invoice.
Feedback
e.g. for commodity indexed prices, if periodic average is taken (e.g. monthly average Crude Oil WTI)