The folks at Tracker I-9 explain how it is supposed to work:
A free E-Verify Self-Check feature that allows individuals over the age of 16 to confirm the accuracy of their U.S. employment eligibility will go live on March 21, 2011 in selected states. The E-Verify Self-Check (Self-Check) phase one roll-out will be available to individuals who currently maintain residency in Arizona, Colorado, Idaho, Mississippi and Virginia, or the District of Columbia. As initial testing and system improvements are made, it is expected that USCIS will expand Self-Check to other states, and eventually be available nationwide.
If the new feature works as expected, individuals will be able to use Self-Check in much the same way as employers use E-Verify, except that individuals will need to take extra steps to verify their own identity. After entering certain biographical information, an independent third party service is used to complete the identity verification process, and if successful, the user is redirected to Self Check to enter additional information in order to complete the employment eligibility check. Self Check will then return one of three results: Work Authorization Confirmed, Possible Mismatch with SSA, or Possible Mismatch with Immigration Information.
If any mismatches are found between the information provided to Self-Check and the governments records, the system will provide instructions on how resolve the issue.
Employers are warned not to use Self-Check to pre-screen the employment eligibility of new hires. If an employer or potential employer asks to see a Self-Check query to prove work authorization, individuals are instructed to notify the Department of Justice, Office of Special Counsel for Immigration-Related Unfair Employment Practices at 800-255-7688. Also, a positive Self-Check result does not guarantee that individuals will pass through E-Verify without issue at a later date.