You can set a default URL for Instant Payment Notification in your Amazon Payments Business account. Or, you can set this value in the user interface when you create an Amazon Simple Pay button. You can accomplish the same thing by setting the
ipnurl parameter in the Amazon Simple Pay button form.
You should periodically test your URL for Instant Payment Notification. Check that the processing script is running on the server and that you can reach the server from the Internet using the fully-qualified domain name in the URL. If you do not receive notifications from IPN, contact Amazon Payments for assistance.
For information on the Amazon Payments business account, see the Amazon Simple Pay Getting Started Guide. For information on creating buttons, see Creating Button Forms Dynamically.