The three types of inventory management systems are manual, periodic, and perpetual. In a manual system, teams count stock by hand and update records on paper or in spreadsheets. In a periodic system, staff members record stock at a single point in time—say, monthly or quarterly—typically using barcode scanners and inventory software. In a perpetual system, machines continuously scan shipment tracking numbers, barcodes, or RFID tags to track inventory movement, and the inventory management system is automatically updated as goods are received, ordered, picked, and shipped.