Security Clearance Improvement Act of 2021 This bill requires the Office of Personnel Management to revise Standard Form 86 (Questionnaire for National Security Positions) to specifically include questions regarding an individual's (1) affiliation with organizations or movements that spread conspiracy theories and false information about the U.S. government, and (2) participation in the activities that occurred at the U.S. Capitol on January 6, 2021, or in similar activities.