At the time when we released Microsoft Dynamics NAV 2009 R2, Microsoft Dynamics NAV 2013, and Microsoft Dynamics NAV 2013 R2, all supported client and server operating systems were tested. However since that time, Windows Server 2012 R2 has become available.
Over the last few months, the Microsoft Dynamics NAV team has been testing the compatibility, and we are now proud to announce that Microsoft Dynamics NAV 2009 R2, Microsoft Dynamics NAV 2013, and Microsoft Dynamics NAV 2013 R2 are compatible with Windows Server 2012 R2!
For more information, see the latest version of the System Requirements in the MSDN Library.