Which identity attribute is NOT required in an identity profile?

In an identity profile, certain attributes are required for effective identity management, while others may be optional. The identity attribute that is not typically required is the phone number. While having a phone number can be beneficial for contact purposes or for two-factor authentication, it is not universally mandated across all identity systems.

On the other hand, attributes such as last name, email, and user ID are generally essential for uniquely identifying an individual within an identity management system. The last name helps to categorize and differentiate between users, the email serves as a primary means of communication and often as a login identifier, and the user ID is a critical unique identifier assigned to each individual, which is fundamental to system operations and user access tracking.

Therefore, the absence of a phone number does not impede the functionality of an identity profile as significantly as the absence of the other attributes would.