To help prevent accidental data loss, OneNote for Mac does not include a command for deleting entire notebooks. You can close any currently open notebook to remove it from your notebooks list in OneNote, but to delete a notebook and all of its contents outright, you’ll need to remove the notebook file at its source.
Warning: Completing this procedure will permanently delete the entire contents of the selected notebook — including all of the sections, section groups, pages, subpages, notes, images, files, and attachments that it may contain. It cannot be undone. If your notebook has at any time been shared with other people, consider first giving the other authors advance notice that you are deleting the notebook, so that they have the opportunity to back up any important information. To save snapshots of any page in a notebook for backup purposes, see Export notes as a PDF file in OneNote for Mac.
To proceed with the deletion of an entire notebook, do the following:
First, you need to close the notebook. In OneNote for Mac, go to any page of the notebook that you want to delete.
On the menu bar, click Notebooks, point to Notebooks, and then click Close This Notebook.
Next, In Safari or in any other Web browser, go to www.onedrive.com. If necessary, sign in with the same Microsoft account or organizational account where the notebook you want to delete is currently stored.
When you have successfully signed into OneDrive, navigate to the Documents folder for your account.
Note: You might need to navigate to a different folder if the notebook was initially saved to a folder other than Documents.
Move the mouse pointer over the notebook you want to delete, and then click to select the small circle that appears next to or in the upper right corner of the notebook icon.
You'll see a small check mark in the circle next to the notebook.
Click Delete on the OneDrive menu bar.