Part deliveries and part invoices

Reality rarely ships an order in one motion. Every stage of the [Standard] chain works on open quantities — what an order line still owes. A waybill may take part of a line today and the rest next week; an invoice may cover one waybill of several. Each document you raise offers only what is still open, so the chain cannot double-deliver or double-charge by accident. The order's page always shows how much of it is delivered and invoiced so far, which is the honest answer to "where is my order?" at any moment.