Are you talking about an invoicing system included in Cpanel? How much is it? I pay about $15 a month right now for Zoho but am trying to cut all of my monthly expenses down as far as possible with a a baby coming in June. $15 isn't much but it all adds up..
Not, it is not part of cPanel. It is included with Softaculous, but it requires a license. It will tie into WHM, if you are a host/reseller. You can pay monthly ($16) or a larger one time payment ($250)