When the "Item substitution" feature is enabled and items are assigned substitution priorities, Master Planning is designed to always favor the higher-priority item's open purchase orders—even if the lower-priority item has an open purchase order with an earlier receipt date that aligns better with the production order’s requirement.

This behavior is by design, based strictly on item priority. However, introducing a control that allows the system to consider the earliest available receipt date—regardless of item priority—would significantly improve inventory utilization. Such flexibility would enable customers to fulfill production demand more efficiently, reduce wait times, and make better use of available supply.