Hi,
If you know that no further service entry required for your service order during service entry creation of initial 1000 value(ML81N)- you could have create service entry sheet and selected final entry for service entry sheet.
If you sure no further action needed for your service order on invoicing where your GR/IR clearing account maintenance needed- you can rum MR11 for your service order/purchase order.
Regards,
Biju K