A flexible merchandise check-out system utilizes a portable bar code scanner/data terminal as part of an auxiliary check-out station for use during times of peak customer traffic, permitting two or more checkers to empty a shopping cart at once for higher throughput. The check-out system includes separable modules for scanning purchased items and for receiving customer payments, respectively. Customer checks tendered in payment are processable in real time via electronic funds transaction (EFT) orders. Depleted inventory is replaceable using a system wherein replacement inventory items are labeled with bar-coded ultimate-destination information and packed into a container for shipment to a receiving/redistribution center, at which the ultimate-destination information is scanned and decoded to enable proper routing of the replacement inventory items.