Resource-Related Billing (RRB) is a process in SAP Project System (PS) and Sales and Distribution (SD) used to bill customers based on actual costs incurred on a project. The two primary prerequisites for this process are:

1. A Dynamic Item Processor (DIP) Profile: This is the central configuration element for RRB. The DIP profile is assigned to the sales order item and defines the rules for how project costs (e.g., labor, materials) are selected, structured, and summarized to create billable items in a billing request.

2. Project Object Account Assignment: The project objects that incur costs (like network activities) must be linked to a sales order item. An activity-account-assigned network provides a direct and granular link, allowing costs from specific activities to be billed via the assigned sales order item, which is ideal for resource-related scenarios.

B. Released WBS elements, activities, and/or activity elements: While objects must be released to post costs, and costs must exist to be billed, this is a transactional prerequisite for a billing run, not a foundational setup prerequisite for the RRB process itself.

C. A header-account-assigned network that is assigned to a sales order item: Although a valid method for SD integration, it is less granular. Activity-account assignment is the more specific and flexible method that directly supports billing based on individual resources (activities).

1. SAP S/4HANA 2021 Documentation, Project System (PS), "Resource-Related Billing Process": "The basis for resource-related billing is the dynamic item processor (DIP) profile, which is stored in the sales document item... The system determines the costs on the account assignment objects that are linked to the sales document item." This confirms the necessity of both the DIP profile and the account assignment link.

2. SAP S/4HANA 2021 Documentation, Project System (PS), "Account Assignment in Projects": This section details the differences between assignment types. It explains, "In an activity-assigned network, you can assign individual activities to a WBS element or a sales document item." This highlights the granular link provided by activity-account assignment, which is fundamental to the RRB concept.

3. SAP Learning Hub, Course TS412 (SAP S/4HANA Project System), Unit 7: Sales in Enterprise Asset Management and Project System: The course material explicitly states that the DIP profile is the central control element for RRB. It further illustrates that costs are collected on PS objects (like activities) which are account-assigned to a sales order item, presenting activity-account assignment as the standard method for this process.