Investigation tiers vs. clearance levels: what T1, T3, and T5 actually mean
NACI is now Tier 1. Secret runs on a Tier 3. Top Secret and SCI run on a Tier 5. The investigation tier and the clearance level are two different things, and conflating them is the most common mistake in cleared hiring.
Ask someone what clearance they hold and they'll say "Secret" or "TS/SCI." Ask what investigation they're on and you'll often get a blank look, or the wrong answer. The two are related, but they are not the same thing, and the gap between them causes a surprising amount of confusion at hiring time.
The clearance level describes the classified information you're eligible to access: Confidential, Secret, Top Secret. The investigation tier describes the background check that established that eligibility: Tier 1 through Tier 5. One is about the information. The other is about the vetting that got you there. This is the plain-English version of how the tiers work, which tier maps to which clearance, and why "Tier 4" is not more sensitive than "Tier 3" even though the number is bigger.
This is general, factual information for people working in or entering cleared roles. It is not legal, security, or career advice. Position sensitivity, investigation scope, and eligibility are determined by federal agencies and adjudicators under official policy, and specifics change over time. For your own situation, your FSO and the official sources linked at the end are the authority.
The chain nobody explains
A clearance isn't one event. It's a chain, and each link is run by a different part of the system:
- Position sensitivity and risk. The hiring agency designates the job first — non-sensitive, public trust, or national-security-sensitive — based on the duties and the access required. The job drives everything downstream, not the person.
- Investigation tier. That designation sets which background investigation you get. The tier is the scope and depth of the check.
- Adjudication. An adjudicator weighs the investigation against the and the whole-person standard.
- Eligibility. A favorable adjudication grants eligibility at a level: Confidential, Secret, or Top Secret. This is what people call "having a clearance."
- Access. Eligibility plus a need-to-know gets you in. For , access also requires being read into specific compartments.
The investigation tier sits in the middle of that chain. It's the part most candidates can't name, even though it's printed on the form they filled out.
The five tiers
The current model is the Federal Investigative Standards (FIS), approved in December 2012 by the Director of National Intelligence and the Director of OPM under Executive Order 13467, and fully implemented across all tiers by 2017. It replaced a tangle of older investigation types with five tiers that serve three different purposes: HSPD-12 credentialing (physical and logical access), suitability and fitness for federal work, and national security eligibility.
Two of those five tiers are actual security clearances. Tier 3 covers Confidential and Secret. Tier 5 covers Top Secret, SCI, and the Department of Energy "Q" access. Everything else on the list is a suitability or credentialing investigation for a position of trust, not a clearance into classified information.
Why the numbers don't go in a straight line
This is the part that trips people up. The tiers are not a single ladder of increasing secrecy. Tiers 1, 2, and 4 are the public trust and suitability track. Tiers 3 and 5 are the national security track. They're interleaved by number, not by sensitivity.
So a Tier 4 investigation (high risk public trust) is, by the number, "above" a Tier 3 (Secret). But a Tier 4 is not a security clearance and a Tier 3 is. A federal financial analyst in a high-risk public trust job goes through a Tier 4 and never touches classified information. A contractor cleared to Secret goes through a Tier 3 and does. The number describes which standardized investigation you got, not how classified your work is.
Public trust is the single biggest source of this confusion. "Public Trust" positions feel clearance-adjacent because they involve a background investigation and a sensitivity designation, but a public trust determination is a suitability judgment about whether you can be trusted in the role, not an eligibility judgment about access to classified national security information. You can hold a public trust position with no security clearance at all.
The old names people still use
The FIS tiers replaced a set of older investigation types, and the legacy names are still everywhere in resumes, job postings, and recruiter shorthand. If you trained or got cleared before about 2017, you probably know your investigation by its old name:
- NACI (National Agency Check with Inquiries) is now Tier 1.
- MBI (Moderate Risk Background Investigation) is now Tier 2.
- NACLC / ANACI (the old Secret-level checks) are now Tier 3.
- BI (Background Investigation) is now Tier 4.
- SSBI (Single Scope Background Investigation) is now Tier 5.
When a job posting says "must have a current SSBI" or "NACLC required," it's using the pre-FIS vocabulary for what are now Tier 5 and Tier 3. The mapping matters because reciprocity and re-use of a prior investigation depend on the tier, not the old label.
"How often do I get reinvestigated?" — the answer changed
The old rule was periodic reinvestigation on a fixed clock: roughly every five years for Top Secret, every ten years for Secret. That model is being retired.
Under Trusted Workforce 2.0, the government-wide vetting reform that began implementation in 2018, periodic reinvestigations are being replaced by Continuous Vetting (CV). Instead of a scheduled re-check every five or ten years, CV runs automated record checks against criminal, terrorism, financial, and public-records databases on an ongoing basis throughout your period of eligibility. When a check produces an alert, DCSA reviews it, decides whether it warrants further investigation, and acts on it.
DCSA — the Defense Counterintelligence and Security Agency, which conducts the large majority of federal background investigations — has enrolled the cleared population into Continuous Vetting. The practical effect for a clearance holder: your record is monitored in close to real time rather than re-examined on a calendar. The National Background Investigation Services (NBIS) is the IT system being built to tie this together.
For candidates, the takeaway is simple. If your clearance is current and you're enrolled in CV, "my reinvestigation is overdue" is mostly an artifact of the old model. Enrollment in continuous vetting is what keeps eligibility live now.
What this means at hiring time
Three things worth getting right when you're reading a job posting or filling out a profile:
- Match the tier to the clearance, not the number. A role asking for "Secret eligibility" is a Tier 3. A role asking for "TS/SCI" is a Tier 5. If a posting lists a public trust tier (T1, T2, T4), it is not asking for a security clearance, even if it involves a background investigation.
- Your investigation tier drives reciprocity. When you move between agencies or contracts, whether your existing investigation transfers depends on its tier and currency. A current Tier 5 can support a new TS/SCI role without a fresh investigation if reciprocity applies; a Tier 3 cannot, on its own, support a TS role.
- Public trust is not a clearance. If your only federal vetting was a Tier 2 or Tier 4 public trust investigation, you don't hold a security clearance — and saying you do on a cleared-job application is a candor problem under , not a harmless shorthand.
What this looks like inside ClearMatch
ClearMatch models clearance as a tier, not a string — Confidential through TS/SCI and the polygraph layers above it — because that's how cleared hiring actually works. The matcher reasons about the eligibility level a role requires and whether your stated clearance meets it. It does not see your investigation file, your DISS record, or your adjudicative history, and it doesn't need to: the agent's job is to surface roles where your clearance and experience fit, then explain why.
If you're setting up a profile and you're not sure whether your federal vetting was a national security investigation (Tier 3 or 5) or a public trust one (Tier 1, 2, or 4), check the form you filled out. An SF-86 means national security eligibility. An SF-85 or SF-85P means suitability or credentialing. That one detail decides which roles are a real match.
Sources: , , , and . Tier designations and reinvestigation policy are set by the federal government and change over time; for your own case, consult your FSO and the official sources above.