Hi @Stefano Del Soldato Scavino
Thanks for reaching out to the community forum.
I apologize for the inconvenience you have experienced in trying to delete a Microsoft Entra Guest ID account.
It seems that your Microsoft account is still linked to certain subscriptions that prevent you from deleting it, you need to cancel any existing subscriptions before deleting the Guest ID account.
Since you are trying to delete a guest account that is linked to your private account, I assume that you do not have sufficient Privileges of the Microsoft Entra tenant that invited you as a guest. ensure you have the admin roles to delete the resource. You can check user admin roles here.
Also, you may remove the guest account from your private account.
Sign into your private account at https://myaccount.microsoft.com/
Select organizations tab you will see the list of organizations you collaborate which you see in the below picture.
choose the organizations and click on leave to leave the organizations by following on screen instructions.
for more information, please refer the documents below.
https://learn.microsoft.com/en-us/entra/external-id/leave-the-organization
https://learn.microsoft.com/en-us/azure/role-based-access-control/role-assignments-external-users#remove-a-guest-user-from-your-directory
https://learn.microsoft.com/en-us/entra/external-id/customers/how-to-manage-admin-accounts
I hope this answer helps! If you have any further questions, please feel free to ask.
Thanks,
Akhilesh.
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