phpBMS is a true open source business management software. If you are a freelancer, you can keep information about clients, keep track of orders and mail PDF bills. For example a freelance web designer/developer can create product categories such as design, setup and coding. Under these categories, products could be analytics, domain and hosting setup, etc…  with associated prices. After you have entered your clients details and product listings, creating a bill becomes easy. phpBMS is a web based solution which you can easily integrate with your existing system. Hope it helps you bill clients more efficiently.