OneNote 2013 builds on the file format first introduced with OneNote 2010. The OneNote 2013 file format is named “OneNote 2010-2013 notebook format,” to let you know it’s compatible with the OneNote 2010 file format.
The OneNote 2007 format is supported in OneNote 2013 so people can work together in different versions of OneNote.
About the OneNote 2013 file format
When you create a notebook in OneNote 2013, it’s automatically saved in the new 2010-2013 file format. You’ll need this format if you want all the features in OneNote 2013, like math equations and linked notes, to work properly.
Note: OneNote 2007 can’t read files created using the 2010-2013 file format, but OneNote 2013 can open and view notebook files saved in the older 2007 file format. To edit, you'll need to upgrade to the latest version. If you’ve already upgraded a notebook to the 2010-2013 file format and you need to revert to the older 2007 format, you can convert the notebook back again.
If you’re upgrading from OneNote 2007 to OneNote 2013, your existing notebooks in the 2007 format won’t be automatically converted. This is to make sure you can use OneNote 2013 for all the notes you’re currently working in, including collaborative projects with people whose shared notebooks are saved in the older format.
Tip: If sharing notes with people who use OneNote 2007 isn't important to you, it’s best to upgrade to the latest version of OneNote so you can enjoy all of the features of OneNote 2013.
To check which file format a notebook is saved in:
In OneNote 2013, open a notebook, and look at the title bar of the OneNote window. If [Compatibility Mode] is shown next to the notebook name, then the notebook is saved in the older 2007 format.
In OneNote 2010, click File > Info. Next to the name of the notebook you want to check, click the Settings button, and then click Properties. In the Notebook Properties dialog box, look at the Default Format to see what format the notebook is saved in.