The best solution is WHMCS + Kayako
WHMCS for Billing stuff, and Kayako for Support!

But, if you don't have budget for Kayako Support Suite, then WHMCS Support should be fine too.

I would go with WHMCS the new v4 is very well made, we used ModernBill in the past for one project and had nothing but problems ...

We have recently switched to WHMCS and could not be happier. After less than a week we decided to purchase the license.

I have to agree with a lot of people here, WHMCS is a great piece of software and I can only recommend it.

It's really up to you. I've used them all and even try others from time to time for different projects & I always end up with either a in-house system or WHMCS.

So take a look at them all, but I'm sure after a WHCMCS trial you'll have no need to change. Also keep in mind that while it's encoded WHMCS is fully expandable in that it really has no limits to what can be done.

WHMcs is really great I think there number 1. Top of the line.

WHMCS is all we use. We tried all the others but WHMCS won in the end.

Another vote for WHMCS! 100%

WHMCS seems to get famous graduately...

WHMCS seem to be the best billing system so far. We had no problem with this system. Other systems we tried are Clientexec, that system is great too, but WHMCS had more user friendly tools.

I love ubersmith it allows you a lot of room to grow and is easy to implement. The email features are easier to setup and maintain the ones in whmcs. The way whmcs routes emails to departments is limiting and cumbersome.

I heard some guy in other forum and he said that the ihost billingf software is great too.

ModernBill is just too resource intensive. I would go with WHMCS. Everything you need is a included with the billing system.

I have used both Modern bill and WHMCS. WHMCS is better than Modern bill and it has great features to manage clients.

WHMCS is the best among them all. It's very feature-rich.