Microsoft Dynamics NAV Application Server (NAS) is a middle-tier server component that executes business logic without a user interface or user interaction. In NAV 2015, NAS is one of the client services that runs in the Microsoft Dynamics NAV Server.

NAS is essentially an automated user client. Because NAS is effectively a non-UI version of the standard NAV client module, it can access all of NAV's business rules.

Error messages that are generated by a NAS process are logged in the Event Viewer.

NAS operates essentially the same as any other NAV Windows client. If setup to run the JobQueue, it processes requests in the queue one at a time, in the same manner as the GUI client. Therefore, as developers, we need to limit the number of concurrent calls to a NAS instance as the queue should remain short to allow timely communications between interfaces. In NAV 2015, multiple background sessions can be started from client sessions. This provides opportunities for NAV automation for the creative designer/developer.