invoice print during cash sales process

Hi,

I am relatively new to SD module. I am working on cash sales process in IDES. when I create the sales order system automatically creating the delivery.

Normally in cash sales process once you create the sales order is created delivery will be created and invoice is also printed. In my case invoice is not getting printed. I checked in spool SP01 also. there also nothing is there. We need to make any extra settings for this ???. Can somebody guide me. where the smart form of the print and print program are assigned so that system automatically triggers the invoice print during sales order creation.

Thanks

Kumar