Authorize.Net is a world known and trusted payment solution to process credit cards online.
How can I obtain an Authorize.Net merchant account?
You can sign up for an Authorize.Net account on their web-site at http://reseller.authorize.net/application/?id=5555901
How to setup Authorize.Net
Open your Control Panel, System Settings -> Payment page
Locate 'Credit card' payment method, in 'Payment Processor' column click 'Change', select Credit card:Authorize.Net SIM, click 'Apply'
Open 'Account Details' and follow the instructions in the popup window
Click 'Save', then 'Enable' to activate this payment method
Save your changes on the payment page.
How to add your Relay Response URL in the Authorize.Net Merchant Interface
Please refer to this article: support.authorize.net/authkb/index?page=content&id=A558
What are the API Login ID / Transaction Key and how to generate them?
Please refer to these articles:
What is the MD5 Hash Security Feature and how to setup it?
Please refer to this article: support.authorize.net/authkb/index?page=content&id=A588
"Authorize.net FDC Merchant ID or Terminal ID is incorrect" error
This is a non Design-Editor error. It indicates an issue with merchant server provider who set up your Authorize.net account or with the Authorize.Net account itself. Please report this error to Authorize.net customer support for help.
The "(123) This account has not been given the permission(s) required for this request" error
Please make sure that you use the correct Login ID. You should use your API Login ID, not the Login ID you use to log in to Authorize.net.
The "(99) This transaction cannot be accepted" error
This error means that the Authorize.Net account credentials you have put into the account details of Authorize.Net payment method in your store's control panel are not valid.
Please, check that the Transaction key is matching your Authorize.Net account.
To obtain your current transaction key:
Log into your Authorize.Net account at: https://secure.authorize.net/
Click on Settings and Profile in the main menu
In the Security section, click Obtain Transaction Key
Enter your Secret Answer (the answer to the Secret Question configured at account setup)
To disable the old transaction key, click to select Disable Old Transaction Key
Note: If the Disable Old Transaction Key box is not checked, the old transaction key will automatically expire and become invalid in 24 hours.
Once you obtain a new key, copy it over into the Transaction key field in the account details of your Authorize.Net payment method in the control panel → System settings → Payment.