Revenue Account for Sales Item

Dear Expert,

Currently I use SAP 8.82 PL06, when I add AR Invoice I choose the same items but some customers have default revenue account and some customers don't have default revenue account, so I need to select it manually. the question is how can I get default revenue account for all customers???

Note: Item GL manage by ITem Group and In Item Group already define the default revenue account.

Best regards,

CHAMNAN