AWS Tasks that Require Account Root User
The tasks listed below require you to sign in as the account root user. We normally recommend that you use a standard IAM user with appropriate permissions to perform all normal user or administrative tasks. However, you can perform the tasks listed below only when you sign in as the root user of an account.
Modify root user details. This include changing the root user's password.
View your account's billing information. For information about how to enable billing access for IAM users see Activating Access to the Billing and Cost Management Console
Submit a Reverse DNS for Amazon EC2 request. The "this form" link on that page to submit a request works only if you sign in with root creds.
Create an AWS-created X.509 signing certificate. (You can still make self-created certificates for IAM users.)
Change the Amazon EC2 setting for longer resource IDs. Changing the setting as root affects all users and roles in the account. Changing as an IAM user or IAM role affects only that user or role.
