Performing an internal Microsoft 365 admin takeover can be a complex process, but it's important to know how to do it in case of an emergency or a change in personnel. Here's a step-by-step guide on how to perform an internal Microsoft 365 admin takeover:
Before you proceed with the admin takeover, make sure that you have the necessary credentials to access the Microsoft 365 admin center. You will need to have global administrator permissions to perform this task.
Log in to the Microsoft 365 admin center using your global administrator credentials. Once you're in, navigate to the "Active Users" section under the "Users" tab.
In the "Active Users" section, select the user account that you want to take over. Click on the account name to open its details page.
On the account details page, click on the "Roles" tab. Scroll down to the "Roles" section and click on the "Global administrator" role. Then click on the "Edit" button.
On the "Edit Role" page, remove the previous admin's access by clicking on the "X" next to their name. Then add your own account by typing in your email address and clicking on the "Add" button.
Click on the "Save" button to save the changes. You should now have full access to the Microsoft 365 admin center as a global administrator.
Log out of the Microsoft 365 admin center and log back in using your own credentials. Navigate to the "Admin" section to ensure that you have full access to all the features and settings.
Performing an internal Microsoft 365 admin takeover can be a delicate process, so it's important to make sure you're following all the steps correctly. If you have any questions or concerns, do not hesitate to contact Microsoft support for assistance.
If you are an admin and want to take over an unmanaged tenant created by a self-service user signup, you can do this with an internal admin takeover.
https://docs.microsoft.com/en-GB/microsoft-365/admin/misc/become-the-admin?WT.mc_id=365AdminCSH_inproduct&view=o365-worldwide
A self-service sign up for any cloud service that uses Azure AD will add the user to an unmanaged or "shadow" Azure AD directory and create an unmanaged tenant. An unmanaged tenant is a directory without a global administrator. To determine whether a tenant is managed or unmanaged, please see Determining Tenant Type.