I think WHMCS still stays on the top of the list when it comes to webhosting billing systems. I personally like the interface and the features it comes with.
We were a long time WHMCS user but since their last price increase we bailed and developed our own. The ability to customize EVERY aspect of the checkout process is priceless, we've never looked back. With integration into our backend the staff has been in love with the new setup, love at first sight shall we say...? LOL
+1 for WHMCS also. I’ve looked and tried other billing solutions but can’t get on with them. The functionality wit’s WHMCS and how it works is great for us.
Webhost Billing System (WBS) is software written in PHP code. WBS includes a complete Front End (user web interface) written in XHTML/CSS web code. The Front End can be used as your website or in portal mode as a separate client portal. The Front End is decoded for full customization of the look. WBS will communicate to your configured payment gateway(s) to perform live payments while customers place orders. Once orders are placed, WBS will then communicate to your configured registrar, hosting server or re-seller hosting account to complete the orders automatically