which billing software is used by "pkwebhost.com" website

That's WHMCS

thanxs....

Be even better if it was a licensed version...
"This domain is not authorized to be using WHMCS.
Please report the url to the installation to us here"

Yeah good find Bear, Also that version looks bit older.

Yeah, that's WHMCS alright. I agree with @bluemediaprint, the portal theme that they are using is very outdated. Checkout demo.whmcs.com to see the latest portal theme, it has some pretty slick icons.

thanxs for your help

Thanks to bear for notifying us about this unlicensed installation. A DMCA notice has been issued for it.

Matt