OE shipment is not posting GL entries if Invoice option is unticked

Hi,

The OE shipment entry is not generating GL entries if the invoice tick box is unselected. If Invoice option got selected, then invoice entry and GL entries are being posted to respective modules. How do I set the system to allow to post the GL entry only for shipment. If invoice posted later, then Invoice will be moved to AR module. Any suggestion much appreciated. 

SAGE 300 2016 version.