It is possible to create a PO Line without inventory by using the "Order without Inventory" option in the Acquisitions area of Alma. When creating such an order, Order Heading, Alternative Heading, and Description are all required fields. However, these fields are not editable after the order is created, so if you make a typo or there is a change to the name of a service (or whatever it is you are ordering), it is not possible to update that information in the heading. Ex Libris should make these fields editable after the order is created.