Do you need license, if you use retention tags on shared mailboxes

[Rhuttunen]

What is the licensing requirement if we want to apply retention tags to shared mailboxes?

Is there any option to apply retention tags to shared mailboxes without licensing, as shared mailboxes by default do not have any license.

If no free option, what is the minimum license requirement?

[#2]

For Exchange retention tags with Delete action, you shouldn't need a license. For tags with Move to Archive action, you will need Exchange Online Plan 1 or equivalent, this is a requirement for having the Online archive enabled. For M365 retention policies/labels, you need a matching "compliance" licenses.

[#3]

@Rhuttunen 

No license for the case, applying retention policy may help