All the non-customer-facing systems within an enterprise, including enterprise resource planning (ERP) and materials/manufacturing resource planning (both referred to as MRP) systems, financial, billing, accounting systems, and human resources (HR). These systems could include and produce secure e-commerce software that processes company information (e.g. a database). A back-office system would maintain a record of the company’s sale and purchase transactions and update the inventory as needed. In addition, the back order system would produce invoices, receipts, and reports.