Anybody knows free billing software with Plesk Control Panel?
I have a reseller account.

What does your reseller provider offer? Not to say anything derogatory about Plesk, but I would have went with an H-Sphere provider for reselling. You can create multi-platform plans across windows, sharepoint, linux, freebsd etcetera along with included ticketing system and billing system already built in.

Check here: http://www.webhostingtalk.com/showthread.php?t=580131

May be http://www.phpcoin.com/ - but I am not sure that it will be integrated with your Plesk 9

Anybody knows free billing software with Plesk Control Panel?
I have a reseller account.

I thought Plesk has buil-in billing system?
You should check with your host to see if they offer free billing script or at discount price.

Check with your provider if they have any type of billing software that they can give you.

If you're able to switch to cPanel/WHM - you could try with BillingReptile.com