No any additional feature is required to start BUSY Inventory management. By default it can be enabled.
But some of the important features if you required to maintain the inventory.
1. Material centre/ Ware house management
2. Serial number/Batch/Parameter/MRP etc. you can maintain the inventory with second level if required
3. You can manage the Inventory with order management, challan management, Quotation management, Invoice, BOM etc if required
4. Define the Minimum/Reorder/Maximum stock control settings
5. Post the transctions
6. Evaluate the neccessary report as per your needs. Some of the important reports are stock ledger, Stock status, Stock analysis, MIS etc.