Authorize.net
Authorize.net Credit Card Billing. For more info see www.authorize.net
The Authorize.net module in WHMCS supports automated captures, recurring billing & refunds from within WHMCS.
Setup
To activate the Authorize.net module in WHMCS, navigate to Setup > Payment Gateways and choose Authorize.net from the Available Gateways dropdown.
Once activated, you can then customise the name to something more friendly such as "Credit Card" and enter the Login ID and Transaction Key corresponding to your Auth.net account
Customer Information Manager (CIM)
The Authorize.net Customer Information Manager (CIM) system allows you to store customers' sensitive payment information on Authorize.net's secure servers, simplifying your compliance with the Payment Card Industry Data Security Standard (PCI DSS).
This works by only storing the full card number on Authorize's system, and not locally in your WHMCS database, and thus even if you were to be compromised, the encrypted full card numbers are not there for any potential hackers to access and potentially use.
To use this with WHMCS, simply activate the Authorize.net CIM module in the gateway configuration area, and deactivate the standard Authorize.net module if already using it, and then the card details will no longer be stored locally in your WHMCS database following each clients next transaction following the activation.
We also have a migration tool available for automatically transferring all your existing locally stored clients credit card numbers over to Auth.net's system should you wish to start using the CIM system retrospectively. The tool can be downloaded @ http://www.whmcs.com/members/dl.php?type=d&id=73
Echeck Module
The Echeck module for Auth.net allows for payments to be processed directly from a bank account. This is a one time payment process only and does not support storing bank account details ot therefore automated recurring billing to the bank account.
To setup, simply activate the "Authorize.net Echeck" option in Setup > Payment Gateways and enter your Auth.net Login ID & Transaction Key along with a custom name for the module where requested. And then that new payment method option will now show in the order process and on invoices for users to choose and make payment with should they choose. No further setup is required.