Requirements

Billic requires the following;

To be installed on the root folder of your domain or subdomain. This means http://yourdomain.com/ or http://billic.yourdomain.com/ or http://clients.yourdomain.com will work.
http://yourdomain.com/billic/ WILL NOT WORK!
PHP Extensions: curl, zlib, mysqli.
PHP Version: 5.1 or later
HTTP Server which supports URL rewriting. Billic works out of the box with Apache by using .htaccess
A cron job that can run BIllic's cron command every minute. Every minute is just a recommendation. If you need to set it to a higher value that is possible.