A billing application is a web, mobile, or desktop application that enables customers to purchase goods and services. Billing applications typically have two sets of users: customers and administrators. Customers use the app to browse products and services for sale, submit orders, pay bills, view transaction history, and rate their purchases. Administrators use the app to configure product offerings (add/remove/update), create invoices or bills (with different payment schedules), track pending transactions (invoices & bills), issue refunds/adjustments, and analyze billing performance metrics such as invoice balance vs payments received etc.