From K Software:
kBilling can process an unlimited number of customers, invoices, products, and services. if you have multiple companies, you can consolidate all of them in kBilling. The program is network-ready, allowing you to access your billing and invoicing information from any workstation on the network. kBilling eliminates the need to type the same information over and over. Enter your customer's contact information once, and retrieve it instantly, when you need to send them an invoice or record a payment. Enter descriptions of the products or services that you offer, and add this information to your invoices with a single click. By making it easy to include information on invoices, you save time and money, and eliminate errors.