SAP Transportation Management (TM) in SAP S/4HANA initiates the transportation planning process based on transportation requirements. These requirements are generated from various logistics documents that signify a demand for moving goods. Stock transport orders represent internal transfer demands, inbound deliveries represent incoming goods from suppliers or other plants, and returns documents (like returns orders and deliveries) represent reverse logistics flows. All three are standard source documents that are integrated to create freight units in TM, which are the basis for planning.

A. Material documents: These are generated as a result of a goods movement posting (e.g., goods issue/receipt), which typically happens after transportation, not as a planning input. C. Transfer orders: These are documents from the classic Warehouse Management (WM) module used for stock movements within a warehouse, not for external transportation planned by TM.

1. SAP Help Portal, SAP S/4HANA 2023, "Transportation Requirement": This document outlines the business documents that can be used to create transportation requirements in SAP TM. It explicitly lists sales orders, purchase orders, stock transport orders, inbound deliveries, and outbound deliveries as sources. The returns process is handled via returns orders and deliveries, which are also supported.

Reference: SAP Help Portal -> SAP S/4HANA -> Transportation Management (TM) -> Order Management -> Forwarding Order Management -> Transportation Requirement.

2. SAP Help Portal, SAP S/4HANA 2023, "Integration with Logistics": This section details the integration points between TM and other logistics modules. It confirms that stock transport orders (MM), inbound/outbound deliveries (LE), and sales/purchase orders (SD/MM) are the primary integration objects that trigger transportation planning.

Reference: SAP Help Portal -> SAP S/4HANA -> Transportation Management (TM) -> Integration -> Integration with Logistics.

3. SAP Learning, Course S4600 - "Processes in SAP Transportation Management": Unit 2, "Transportation Requirements Management," describes how freight unit building rules are applied to transportation requirements originating from documents like stock transport orders, deliveries, and sales/purchase orders.

Reference: SAP Learning Hub, Course S4600, Unit 2: Transportation Requirements Management, Lesson: Creating Freight Units.