Final answer:
SLIT data is necessary when the NIIN has the 'S' (serial number tracking) or 'L' (lot number tracking) Record Type Code assigned, ensuring item accountability and traceability.
Step-by-step explanation:
Serial and Lot Item Tracking (SLIT) data is required if the National Item Identification Number (NIIN) has a Record Type Code of 'S' or 'L' assigned. These codes indicate whether an item needs serial number ('S') or lot number ('L') tracking. This requirement is part of logistics and inventory management practices, commonly associated with military or defense inventory systems but also applicable in other sectors that demand detailed tracking of items for accountability, traceability, and quality control purposes.