Not possible to determine a consumption account

Dear

When i create sales order,it prompts that 'Not possible to determine a consumption account'.

Message no. 06138

Diagnosis

The system was not able to determine a consumption account for the purchase order item with account assignment.

Which account is determined is controlled via Customizing with the function "automatic posting" (transaction/event key GBB).

How can i resolve it?

TKS!

Edited by: stephen chow on Sep 29, 2008 10:30 AM