An SSBI is required for Top Secret, Q, and SCI access, and involves agents contacting employers, coworkers and other individuals. Standard elements include checks of employment; education; organization affiliations; local agencies; where the subject has lived, worked, or gone to school; and interviews with persons who know the individual. The investigation may include an NACLC on the candidate’s spouse or cohabitant and any immediate family members who are U.S. citizens other than by birth or who are not U.S. citizens.