Intercompany sales looks simple in process diagrams: one company sells to the customer, another company delivers, and internal settlement follows. The implementation difficulty comes from the fact that every step touches more than one legal entity.
Sales order responsibility, delivery plant, inventory ownership, customer billing, intercompany billing, tax, revenue recognition, and cost posting all need to line up. When they do not, the problem usually appears as month-end reconciliation work rather than as an obvious configuration error.
What S/4 improvements should not hide
Newer S/4 capabilities can reduce some historical friction, but they do not remove the need for process decisions. Companies still need to define the commercial model, settlement route, document responsibility, and exception handling rules before configuring the flow.
In other words, intercompany sales should be designed from the business contract and legal-entity relationship first, then mapped into SAP documents.