Hi curious7
Check the following conditions before decommisioning tenant :
- You've paid all outstanding invoices and amounts due or overdue.
- No users are in the Azure AD tenant, except one global administrator who will delete the organization. You must delete any other users before you can delete the organization.
- If users are synchronized from on-premises, turn off the sync first. You must delete the users in the cloud organization by using the Azure portal or Azure PowerShell cmdlets.
- No applications are in the organization. You must remove any applications before you can delete the organization.
- No multifactor authentication providers are linked to the organization.
- No subscriptions for any Microsoft Online Services offerings (such as Azure, Microsoft 365, or Azure AD Premium) are associated with the organization.
You can check the Sign in logs if there is any activity that will give you a view if the tenant is in use.
Follow the below link this has everything you need to go through before decommisioning a tenant :
https://learn.microsoft.com/en-us/azure/active-directory/enterprise-users/directory-delete-howto
Hope this helps! Click "Accept as Answer" if it did.