Query in Prepayments in Receivables

[Balasubramanian]

Hi,
I have a query regarding prepayments functionality in receivables.
I have defined a payment term with pre-payment functionality checked.Attached the payment terms to the customer.

Created a receipt source of automatic.
Created a sales order and hence a receivables invoice for the customer.
While tryin to run 'Automatic Receipts Creation Program (SRS)' , i am unable to find the receipt source which i have defined earlier.

Kindly let me know where i am going wrong.
Any pointers will be of great help.