shipped/return document but deleted orders

Hi all,

Which of the settings on a sales header influences the posting process that the order will be deleted after a shipment/return or goods?

We are working with a custom system within the classic client which works with quotes, based on the customer it creates a order with shipment or only a invoice. The same on returning items. We've experienced during the year that some orders are shipped/returned but the order is deleted. As the custom system doesn't delete i've tried looking in the posting process and if there are any variables on the sales header.

Is there a certain variables which states to delete afterwards?

grt,NoiK