Facebook added a new feature to its Facebook Credits API that allows developers to download reports regarding payments in their Facebook applications. The payment reports are generated daily by Facebook. Up until now, developers had been receiving payment reports via email.
Per the Facebook announcement post in the Developers Blog, the new payments reporting API:
Developers can find detailed information on how to use the new payments reporting API in the available documentation.
Developers should also note that the email reporting system will no longer be supported by Facebook effective November 7th, 2012.