In OneNote Online, you can mark selected notes with tags that let you visually identify and quickly return to important items that need to follow up on, remind yourself about, or share with others. You can tag anything from a single line of text to an entire paragraph of notes.
Apply a tag
Place the cursor at the beginning of the line of text you want to tag.
On the Home tab, click Tag.
In the list of tags that appears, click the tag you want to apply. For example, to tag a follow-up question in your notes, click the question mark symbol in the list.
Note: Some tags can be applied side-by-side with other tags. If you want to change an existing tag, first remove it and then apply the new tag you want.
Remove a tag
Place the cursor at the beginning of the line of text containing the tag.
On the Home tab, click Tag > Remove Tag
Removing tags is not only useful for when you change your mind about tags you’ve applied, but it also removes such items from follow-up. In the OneNote desktop app, you can create automatic To-Do lists by searching for your tagged notes. For info about how to do this in OneNote 2016, see Search for tagged notes.