In SAP S/4HANA, MRP usesbackward schedulingto calculate the basic dates for dependent requirements (e.g., components needed for production). Backward scheduling starts from the requirement date of the finished product and works backward to determine when components must be available. The key time elements considered are:

Planned delivery time(A): This is maintained in the material master (MRP 2 view, field: Planned Delivery Time) for externally procured materials. It represents the time required by the vendor to deliver the material, and MRP uses it to calculate the start date for procurement to ensure the component is available when needed.

In-house production time(D): For materials produced in-house, this is maintained in the material master (MRP 2 view, field: In-house Production Time). It defines the total time required to produce the material, independent of quantity, and MRP uses it to determine the start date of production for dependent requirements.

Total replenishment lead time(B) (MRP 2 view, field: Total Replenishment Lead Time) is an optional field that includes all procurement and production times but is typically used as a fallback or for special cases, not as a standard element in backward scheduling for components.Operation duration(C) is specific to routing data (e.g., setup, processing times) and is considered in detailed scheduling (e.g., production order scheduling), not MRP’s basic date calculation, which relies on material master data. This aligns with SAP’s MRP scheduling logic as per official documentation.