For the system to handle an inter-company stock transfer, it needs to treat two parts of your own organization as separate business entities. The supplying plant acts as a vendor, and the receiving plant acts as a customer. This requires a specific master data setup that connects the dots between Materials Management (MM) and Sales & Distribution (SD).

The foundation of this setup in S/4HANA is the Business Partner (BP) model. Instead of separate customer and vendor master records, you have a single Business Partner. This BP is then extended with different roles. For an Inter-STO, you'll create one Business Partner representing the partner company code and assign it both a customer role (for the SD side) and a supplier role (for the MM side). This ensures all data, like addresses and bank details, is consistent across the process. This synchronization is managed by the Customer Vendor Integration (CVI) component, making the BP the single source of truth.

Once the Business Partner is created with the necessary roles, you must explicitly link your organizational structures to these new master data records. This is a two-sided process, touching both SD and MM configuration.

You need to assign the customer number (from the BP's customer role) to the receiving plant. This is done within the context of a sales area (Sales Organization, Distribution Channel, Division). This link tells the system which 'customer' to use when the supplying plant needs to create a delivery and billing document for the stock transfer.

Conversely, from the MM perspective, the supplying plant is the 'vendor' fulfilling the order. You link the supplying plant to the vendor number (from the BP's supplier role) in the vendor master data. This allows the receiving plant's purchasing organization to create a stock transport purchase order against a known internal supplier.

The final critical piece of configuration is defining the shipping data for the plants. This setup is what enables the system to automatically create a delivery document from the stock transport order. Without it, the process would grind to a halt.

In the customization settings for a plant, you must specify the sales area (Sales Org, Distribution Channel, Division) it will use for shipping activities. Most importantly, this is where you assign the customer number that represents the receiving plant. When an Inter-Company STO is created, the system uses this configuration to automatically determine the correct shipping data for the plants and create the outbound delivery document without manual intervention. It knows the 'ship-to party' is the internal customer assigned to the receiving plant, and it uses the supplying plant's sales area to process the shipment.

With these master data connections in place, the system has a complete picture. It understands that the purchase order from one plant is an internal sale for another, allowing for a seamless flow of documents from the STO in MM to the outbound delivery and invoice in SD.

Time to check your understanding of these crucial links.

This configuration establishes the master data backbone for all inter-company stock movements. Getting it right ensures that logistics and financial postings stay perfectly synchronized between the partner companies.