Security Clearance Guide
Everything you need to know about U.S. security clearances — levels, the application process, timelines, salary impact, and what adjudicators look for.
Understanding clearance levels is critical for career planning in intelligence and national security. Each level grants increasing access — and commands a significant salary premium.
Mid-level clearance granting access to information that could cause 'serious damage' to national security if disclosed without authorization.
Access Level
Information classified as Secret and below
Investigation Type
Tier 3 (T3) — National Agency Check, Local Agency Check, Credit Check, Written Inquiries
Timeline
2–6 months
Reinvestigation
Every 10 years
Salary Premium
$10,000–$18,000/year
Common Roles
Intelligence Analyst
Military Officer
Defense Contractor
Law Enforcement (federal)
IT Systems Administrator (DoD)
Key Facts
- The most commonly held active clearance (~3 million holders)
- Required for most DoD contractor positions
- Includes a credit check and criminal background investigation
- Can be sponsored by a government agency or cleared contractor