When a person applies for a security clearance or wants to keep an existing clearance, the United States government conducts background investigations or reinvestigations. This includes filling out an extensive application and undergoing interviews, fact-checking, and criminal checks at both state and federal levels. The applicant's creditworthiness is also assessed. To ensure a successful investigation, the applicant's full cooperation is required, and providing false information could result in the application being denied. There are several reasons why an applicant may be denied a clearance.

If an application is denied, the applicant will not be granted access to sensitive or classified information; however, they typically have the right to appeal the decision. The applicant will receive a Statement of Reasons or a Notice of Determination that explains why they are not fit to have a security clearance. Depending on the agency, the applicant may be allowed to submit a written appeal or have a hearing in front of the federal agency's appointment member.

If the appeal results in a denial or revocation, the applicant typically has the right to appeal to a higher governing agency.