Free Open Source Online Invoice System: siwapp
The application has a slick interface & provides a simple usage to create professional-looking invoices.
Some features of siwapp:
- invoices with different serial numbers can be managed
- invoices can be downloaded as PDF files
- periodical invoices can be created automatically
- & more
siwapp uses MySQL to store data & if you need periodical invoices to be e-mailed automatically, a scheduling system (like cron) must be used.
It can also work as a module (be integrated to other business management applications) with the API support.