CMMC 2.0 Enforcement Is Here: What Happens During a C3PAO Assessment

Executive Brief

Cybersecurity Maturity Model Certification (CMMC) 2.0 is no longer coming; it’s here.

With 48 CFR now in effect, nearly all contractors handling Controlled Unclassified Information (CUI) will have to prove compliance through a Certified Third-Party Assessment Organization (C3PAO).

These independent assessments verify that your organization has implemented all 110 National Institute of Standards and Technology (NIST), Special Publication (SP), NIST SP 800-171 controls required for Level 2 certification.

For many in the Defense Industrial Base (DIB), this is their first engagement with a formal cybersecurity audit. Knowing what happens during a C3PAO assessment can make the difference between certification and costly rework.

Dig deeper below to learn what to expect and how to prepare.

1. Phase 1: Conduct the Pre-Assessment

This first phase determines whether your organization is ready for the formal CMMC Level 2 assessment.

What the C3PAO reviews:

• System Security Plan (SSP): Must be complete, accurate, and consistent with NIST SP 800-171 requirements.
• Assessment Scope: Defined per 32 CFR §170.19(c). Any disagreements about what systems or assets are in-scope must be resolved before moving forward.
• Evidence Availability: The C3PAO confirms that all required artifacts and personnel will be accessible during assessment activities.
• Readiness Determination: The Lead Certified CMMC Assessor (CCA) decides whether your organization is adequately prepared.
• Assessment Team Composition: The C3PAO designates qualified assessors and ensures no conflicts of interest exist.
• Pre-Assessment Form: Completed and uploaded into the CMMC Enterprise Mission Assurance Support Service (eMASS) system.

If your organization isn’t ready, the C3PAO will issue an Adverse Determination of Readiness and may suspend or reschedule the assessment.

2. Phase 2: Assess Conformity to Security Requirements

Once readiness is confirmed, the C3PAO formally evaluates your implementation of the 110 NIST SP 800-171 controls.

Key steps include:

• In-Brief Meeting: Sets objectives, roles, and schedule for the assessment.
• Implementation Assessment: Using the NIST SP 800-171A methods — Examine, Interview, and Test — to validate control effectiveness.
• Sampling for Depth and Coverage: Evidence is reviewed using a focused, non-statistical sampling approach.
• Scoring: Controls are rated Met, Not Met, or Not Applicable in accordance with 32 CFR §170.24.
• External and Cloud Service Providers: Assessors verify that Customer Responsibility Matrices (CRMs) and FedRAMP authorizations or equivalencies are in place.
• Daily Checkpoint Meetings: Provide progress updates and address coordination issues.

This phase determines whether your organization meets all required security objectives.

3. Phase 3: Complete and Report Assessment Results

After testing and verification, the C3PAO compiles and reviews results before reporting them to the Department of Defense (DoD).

What happens:

• The C3PAO prepares a formal Assessment Results Report in the required eMASS format.
• A quality assurance review is conducted by a Certified CMMC Assessor not on the assessment team.
• An Out-Brief Meeting summarizes findings, POA&M status, and the preliminary certification determination.
• Results are uploaded to CMMC eMASS and retained by the C3PAO for oversight.

Possible outcomes include:

• Final Certificate of CMMC Status (all controls met),
• Conditional Certificate (valid POA&M items remaining), or
• No Certificate (if critical requirements are not met).

4. Phase 4: Close Out POA&M and Issue Certificate

The final phase involves the C3PAO formally issuing your certification and, if applicable, closes remaining POA&Ms within the stipulated 180 days.

Activities:                                                                                                                                                      

• The C3PAO generates and signs the official Certificate of CMMC Status (Final or Conditional).
• Certificates are uploaded to CMMC eMASS and shared with the organization.
• If issued conditionally, you may contract a C3PAO to conduct a POA&M Closeout Review to verify remediation and obtain a Final Certificate.

How to Prepare for Success

Preparation begins months before the audit:

• Conduct an internal gap assessment using NIST 800-171A as your reference.
• Ensure your SPRS score reflects actual implementation — not intent.
• Centralize evidence in a compliance platform for faster validation.
• Make sure your POA&M does not include any of these controls.
• Engage a Level 2-certified Registered Provider Organization (RPO) like ISI for pre-assessment readiness.

ISI Insight: Being proactive minimizes costly rework and helps your team stay focused during the audit process.

What a C3PAO Assessment Is — and Isn’t

A C3PAO assessment is verification, not consultation. Assessors cannot guide you on remediation or provide advice during the evaluation. Their role is to independently confirm that your environment meets the required standard.

That’s why working with an RPO beforehand is critical and preparation must happen before the assessment begins.

CMMC 2.0 enforcement marks a major shift for the DIB. C3PAO assessments ensure cybersecurity performance, not just promises.

By preparing now with complete documentation, validated evidence, and clear control implementation, you can move through the process confidently and protect your eligibility for future DoD contracts.

FAQs

How long does a C3PAO assessment take?

Most people think of the 5-day interview week, but that’s only one part of the process. A full C3PAO assessment typically spans 4–6 weeks including pre-assessment review, evidence validation, the 5-day interview period, reporting, and any required POA&M closeout. 

What happens if we fail an assessment?

You’ll be provided with a list of controls also referred to as the Plan of Action and Milestone (POA&M) that were not met. Once addressed, you can request reassessment.

Can we choose our own C3PAO?

Yes. The CyberAB maintains a directory of authorized C3PAOs. Many contractors select firms that align with their size and sector experience.

How long is certification valid?

Three years, with annual affirmations confirming continued compliance.

Internal Links

• 48 CFR Goes Into Effect: What Contractors Should Do Now
• CMMC 2.0 in 2025: What Defense Contractors Are Doing Now
• Understanding SPRS Scores: What DoD Contractors Need to Know
• Choosing the Right CMMC Compliance Software