Abstract: Systems and methods for efficient user authentication in a client-server system using a tiered, risk-based approach including a no-risk tier are provided. When a user requests access to the system for a no-risk feature, the user is registered without an additional authentication test. When the user later requests a higher risk transaction, the user is provided with the appropriate third-party additional authentication test based upon the risk level and applicable vendor profile. During no-risk access to the system, user data is collected that may be used with the additional authentication test at the appropriate time.