Posting service order without creating an invoice


I use the service module of Navision and I have a problem.

When I post a service order, the system automatically creates an invoice (to post a service order, you must fill at least one “service invoice line”).

The problem is when I create a service order from a contract, I don’t want to create any invoice as it’s free of charge for the customer (cost is included in the invoice of the contract!). On the other hand, if I don’t post the order, I won’t have the “next planned service date” automatically updated by the system…

My question: is it possible to post an order without filling “service invoice line” and/or without having an invoice at the end?

Thanks a lot for your answers dear users…