This is a fully functional payment gateway for Authorize.net. US merchants can sign up for an account with authorize.net here, UK merchants can now do so here. Supports recurring payments, free trials, and setup fees.
If you have an SSL certificate installed, and your order forms etc. are served over https, this gateway will communicate directly with authorize.net, and the customer will never leave your site. If you do not use SSL, the customer will be redirected to authorize.net's secure server for credit card detail capture and authorization (note: recurring payments cannot be taken unless you use SSL - authorize.net does not allow subscriptions to be set up by redirecting the customer to them). Authorize.net does not reliably send callbacks to confirm payment if you do not use SSL, so invoices might not be marked as paid automatically. It is therefore strongly recommended that you use an SSL certificate with this gateway, and set the 'Use SSL for ALL pages?' option to 'yes' in nBill global configuration.
Recurring payments have a maximum subscription length of 3 years (imposed by Authorize.net) - if you select to have the gateway update the order expiry date (there is a parameter that allows this), it will set the expiry to either the card expiry date, or 3 years' time - whichever comes first.
If you are NOT using SSL, the only way to return the user to your site after payment is to use the authorize.net hosted receipt page and supply a link on there to return to your site. You can do this by logging into your merchant control panel at authorize.net, selecting Account->Settings->Receipt Page->Receipt Method, and entering the following URL (where www.example.com is your actual website address):
Do not try to use a relay URL nor a silent response URL, as these do not work properly due to limitations in the way authorize.net works and the way nBill can receive callbacks through Joomla.
This is an nBill extension. Use the extension installer in nBill to install it.