If you’re looking for a billing system which is easy to set-up and use, WHMCS might be one of your preferred choice to give a try. It has simple setup and integration, and once you’ve set it up, all packages are quite easy to restore and maintain. WHMCS follow the industry standard, and uses excellent template system which is just simple whenever you would like to change the header and footer files.

WHMCS isn’t constrained to just web hosting, You can sell all kinds of tangible or intangible products integrating a shopping cart and add configurable options for dedicated servers and custom fields for additional data. It is best billing & support solution for Web Hosts & Other Online Businesses. Some of the feature here which make it truly a powerful billing system.

whmcs

* Easy to Use Client Area with Integrated Support Tools
* Fully Customisable Client Area with a Powerful Templating System
* Automated Hosting/Domain Provisioning & Management
* Payment Tracking, Accounting Features & Statistical Report
* Automated Recurring Credit Card Billing
* Development Kits, Action Hooks & an API for integrating & extending
* Automatic invoice generation x days before items are due, reminders and overdue notices all automated
* Ability to create one-off invoices – ideal for web design/consultancy firms
* Automated Recurring Billing & Simple One Time Invoicing
* Flexible Product Options, Custom Welcome Emails, Fields & Options
* 3D Secure (Verified by Visa & Mastercard SecureCode) for gateways that support it (ProtX & Quantum Gateway)
* PDF Invoicing Support
* Automated credits on overpayments and application to invoices
* Account Prefunding Option for Clients
* Clients can order upgrades/downgrades to their products & services from the client area
* Promotions support both one time & recurring, fixed value or percentage incentives
* Offer Free Domains when bought in conjunction with certain packages/billing cycles
* Tax Support with ability for Multiple Tax Zones & Tax Exemptions

I have just added few important features above however their feature is not just limited to this, to check more about their feature and support tools you may wish to check their main website.