Duplicate company in AX 2012

The Duplicate Company function in AX 2009 is deprecated in AX 2012, and the reason is "The organization model represents a paradigm shift in Microsoft Dynamics AX 2012", said by Microsoft. To copy a company in AX 2012 for demo or test, now you'll have to

1. create a definition group
2. export the def group from old company
3. import the def group to the new company

When you create def group, go to Include table group tab and make sure you've selected the tables you want to bring into your new company. When you import, go to the Advanced tab and select/deselect the Include shared tables checkbox as it's needed. Microsoft has a very detailed tutorial on this process:

Use Microsoft Dynamics AX to transfer (export and import) data [AX 2012]