The freebil Drupal 7 module is intended to serve as a mini billing system for small businesses or individuals. It was first conceived as an accounting tool for online freelancers. It tracks customers, contacts, invoices, and payments. All customer, invoice and payment data is entered by the user via forms. An HTML invoice is generated which can be emailed to the customer. As payments are received, the user enters the payment data and the balance due is updated. A new invoice can be generated if there is still an outstanding balance.
The data model: