The registration module sends the recurring billing transaction to the AIM/ARB api at auth.net. Auth.net does the recurring billing to the customers credit card after that. The module has a silent postback feature where auth.net notifies the module if a credit card declines and removes the user from the role they were added to when they originally purchased. That feature is called a silent postback at authorize.net. The registration module has separate modules that allow the user and portal admin to cancel subscriptions.

Please see our registration module page and users guide for a detailed description of recurring billing features

http://www.smith-consulting.com/products/dotnetnukemodules/registrationmodules.aspx