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 and accounting systems, human resources (HR). These systems can include/produce secure e-commerce software that processes company information (e.g. a database). A back-office system will keep a record of the company’s sales and purchase transactions, and update the inventory as needed. Invoices, receipts, and reports can also be produced by the back-office system.