If you can't share or collaborate in the Notes app on your iPhone or iPad - Apple Support

To share or collaborate in the Notes app, everyone needs an Apple device with the latest operating system and enough storage. You can also use iCloud.com.

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How to collaborate with others in Notes on iPhone, iPad, and iPod touch — Apple Support

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Share Freeform boards and collaborate on iPad - Apple Support

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iPad User Guide - Apple Support

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Share Freeform boards and collaborate on iPhone - Apple Support