Have you ever wondered what a Certified Third-Party Assessor (C3PAO) is really thinking during your CMMC compliance assessment? Imagine this: Day 1 of your CMMC Level 2 assessment, the assessor scans your policies and suddenly asks, “Can I see the sign-in log from your last HVAC repair visit?” If you’re thinking “Why on earth the HVAC log?” you’re not alone. In fact, that very question came up in a recent retrospective our team held after guiding a client through a CMMC assessment—and it revealed a lot about how assessors approach their job.

In this post, we’ll step into the assessor’s shoes and explore how they interpret NIST SP 800-171 objectives, what they look for in evidence quality vs. quantity, how they deal with POA&Ms (Plans of Action & Milestones), and which behaviors and documentation signal a truly mature cybersecurity program.

These insights come straight from real CMMC assessment experiences (including our support of a large enterprise CMMC journeys) and our post-assessment retrospectives. By the end, you’ll not only know what to expect from a C3PAO assessment—you’ll also pick up tips to prepare so well that you’ll impress your assessor and ace your audit.

C3PAOs Don’t Just Verify Controls—They Validate Capability

A C3PAO assessor’s job isn’t to confirm that every NIST 800-171 control is written in your policies—it’s to confirm that your organization lives out those controls. For example, NIST 800-171 (and by extension CMMC) includes requirements for physical security. It’s one thing to state “We escort visitors and log repairs” in a policy. An assessor may smile at your policy and then say: “Prove it.”

In a recent post-assessment retrospective, our team noted that the assessor asked to see the sign-in records for the last HVAC repair contractor to confirm the company followed its visitor escort procedure. This wasn’t because the assessor particularly cared about air conditioning; it was a spot check to see if policy meets reality.

In the assessor’s mind, if you claim to control facility access, an objective is “unauthorized people are kept out.” How do you prove that? By showing evidence like a real visitor log with dates, names, and escort signoffs. No log equals a gap in meeting the objective, even if the policy sounds good. Accessors are looking for evidence of implementation, not just documentation. For example:

• A policy that states MFA is required is good, but logs showing consistent enforcement are better.
• An access control policy is expected, but screenshots, access reviews, and system settings prove it’s real.

The best way to think about it? Assessors are looking for operational truth, not paperwork compliance.

Lesson learned: The strongest performers are those who can tie every control to an operational habit—something they really do, not something they hope to do by assessment week.

2. Know Your Scope and Boundary

The focus on objectives also means assessors will consider the context of your environment so long as you make it clear to them. A savvy assessor knows that not all controls apply equally to every scenario. If your entire IT is cloud-based with no on-premises servers or data centers, many physical security controls can be inherited from your cloud provider or marked not applicable. It’s wise to clarify your scope early so the assessor doesn’t waste time on irrelevant checks.

One of our C3PAOs emphasized the importance of “scoping out your environment as much as possible.” For instance, if you have no on-prem assets, point that out so everyone understands that physical asset controls are largely handled by (say) your cloud datacenter provider.

Good assessors will adjust to your scope. Less experienced assessors might still ask every question “by the book” so it’s in your interest to politely educate them about your architecture upfront. Either way, be prepared to discuss why certain controls do or don’t apply in your situation as it demonstrates that you understand the intent of the framework.

Lesson learned: If your setup is unusual or scoped in a specific way, make sure you communicate that clearly. You’ll impress an assessor by demonstrating a grasp of the “why” behind each control—and you may prevent unnecessary questioning about controls that don’t apply.

3. Quality of Evidence Matters More Than Quantity

It’s tempting to over-prepare by dropping every document you can find into a compliance folder. But C3PAOs aren’t impressed by volume—they’re looking for clarity, traceability, and relevance.

One mistake we often see is outdated or inconsistent evidence. If your policies or system settings changed mid-project, make sure your evidence reflects those changes. In the heat of an assessment, nothing irks an assessor more than discovering, for example, that you updated a security control, but forgot to update the evidence.

In one case, our team realized during an assessment that an important piece of evidence hadn’t been updated. The assessor noticed the terminology mismatch and immediately flagged it—essentially saying, “Wait, your evidence doesn’t show the new approach you claim to use.”

After resolving the issue, a lesson was learned: keep your evidence repository fully in sync with your current environment and practices. Stale evidence (even due to a small wording change) can shake an assessor’s confidence. Good evidence tells a story:

• What control is being met?
• Who owns it?
• When was it last validated?
• Where is it implemented?

If an assessor must dig through hundreds of files to piece that together, you’re introducing risk and confusion.

Lesson learned: Streamlined evidence mapping—ideally in a single, indexed repository—saves time and proves maturity. A mock assessment can help you identify which artifacts are too weak, redundant, or missing context.

4. POA&Ms: The Last Resort

Even with great preparation, achieving 100% compliance with every control by audit day isn’t always possible. Maybe a new technology control is in progress, or a policy was recently approved, but not fully enacted. Under CMMC (particularly the newer 2.0 version for Level 2), there is room for a limited number of POA&Ms (Plans of Action & Milestones) to address minor remaining gaps after the assessment, so long as they’re not critical controls and are resolved in a defined timeframe.

How Assessors View POA&Ms

From the assessor’s perspective, POA&Ms should not be used as a substitute for readiness. A seasoned assessor will not view a POA&M as a free pass. If too many findings are deferred to POA&Ms, or if the items are high-risk, it signals that the organization may not be truly prepared. In fact, an assessor might question your maturity if presented with a laundry list of POA&Ms for basic requirements. Ideally, most controls should be fully implemented at assessment time, with POA&Ms reserved only for lower-priority items that genuinely need a bit more time.

Preparation Is Key

In our experience working with clients, we advise treating a formal CMMC assessment as the finish line, not a starting point for compliance work. That means leveraging internal audits or mock assessments well in advance to identify gaps and remediate them before the C3PAO comes in. By the time the assessor arrives, you want as few “open items” as possible. Not only do CMMC rules limit how many POA&Ms you can have and which practices are eligible for deferral, but accessors also differentiate  between organizations that that nearly meet the requirements and will finish a couple tasks later, versus one that clearly hasn’t put in the effort and is relying on promises. The former may receive a recommendation for certification once POA&M items are resolved, whereas the latter may face heavier scrutiny or even risk a failed assessment if the gaps are too significant.

How POA&Ms Are Evaluated During Assessment

Typically, if a control is not met, the assessor documents it as a finding and discusses it with you to understand why. This is your chance to present any mitigating factors or ongoing work. If it’s an allowable POA&M item, you can propose a Plan of Action: what will be done, who’s responsible, and by when. Credibility and specificity matter—a vague promise like  “We’ll improve our encryption, someday” won’t cut it. A solid POA&M would be more like: “Deploy FIPS-validated encryption module version X to all endpoints via update by Q4 2025; currently in testing phase.” Assessors appreciate seeing a drafted POA&M at assessment time, as it demonstrates proactivity; they may even include your proposed milestones in their report.

Assessor Accountability & Risk Considerations

It’s also worth noting that assessors themselves must justify any POA&M in their report to the CMMC accreditation body, following strict guidelines (e.g., no more than 10% of Level 2 practices, and none of the highest-weighted ones, according to CMMC 2.0 rules). They are quite literally thinking in terms of risk—both security risk and compliance risk. A significant security risk cannot be deferred with a POA&M, and too many low-risk items can also be problematic. Ultimately, assessors ask: “Is this organization substantially compliant, with only minor adjustments needed?” If yes, POA&Ms are acceptable. If not, they might recommend you fix issues and reconvene.

Lesson learned: In our experience, keep your POA&Ms to an absolute minimum and make sure you are proactively managing any that you have. Don’t bank on POA&Ms to save you. An assessor views them as an exception, not a checklist.

5. Maturity Includes Behavior, Not Just Systems

CMMC isn’t just about compliance, it’s about maturity. Assessors, therefore, look beyond whether requirements are met—focusing instead on how you meet them and whether security is woven into your organization’s culture and habits. This is somewhat subjective, but there are clear signals that scream “mature organization” to an assessor in terms of both behavior during the audit and the quality of your documentation and processes.

Consistency & Confidence

One of the biggest tells of a well-prepared (and well-run) organization is how consistently its team answers the assessor’s questions. For example, if both your IT admin and manager are asked about account provisioning, their explanations should align. Inconsistent answers raise concerns that policies aren’t truly adopted, or that different teams aren’t on the same page. Nothing erodes an assessor’s confidence faster than contradictory answers from different representatives of your company. To the assessor, inconsistent answers raise concerns that policies aren’t truly adopted, or that different teams aren’t on the same page.

A great practice to demonstrate maturity is ensuring all key team members know your security policies and System Security Plan (SSP). We have found it critical that technical teams, like MSP operations teams, fully comprehend what is in the SSP and where to find the proof points or evidence for each control. This way, when an engineer is asked, “How do you handle removable media?” they know both the daily practice and the official policy. That alignment is pure gold. We started conducting internal trainings so everyone—from compliance leads to technical support staff—knows exactly which evidence or process corresponds to each requirement. When your whole team is singing from the same hymnal, assessors definitely notice. It exudes credibility.

Professionalism & Preparation

How your team conducts itself during the assessment interviews matters. While assessors do not score demeanor directly, professionalism stands out. For example, being well-organized with proper documentation—like having an evidence binder or digital folder ready—shows you are prepared and demonstrates maturity. Responding to questions thoughtfully and not defensively is another. If an issue is found, a mature response might be: “Thanks for catching that—let’s discuss how we address it,” rather than dismissing the concern with “Oh, that’s not a big deal, do we really have to fix it?” The former shows you take security seriously; the latter might suggest to the accessor you’re trying to skate by.

Another behavior to note is how your team handles not knowing an answer. No one expects every individual to know everything, but a mature team checks for accuracy rather than guessing. If you are unsure, say, “Let me verify that and get right back to you.” Assessors respect this approach. In our internal reviews, we emphasize that if an assessor throws a curveball, it’s perfectly fine to take a brief pause, huddle as a team in the background (we often use a quick chat channel during virtual assessments), and come back with a verified answer. This prevents conflicting responses and demonstrates team composure under audit pressure. Practicing mock Q&A sessions ahead of time also builds team confidence.

Lesson learned: Build confidence with staff by practicing these interactions through tabletop exercises, clear policies and procedures, and internal interviews. Familiarity with assessment interviews can transform nerves into readiness.

Final Remarks

CMMC is more than just passing audit—it’s about proving your organization can protect sensitive information every day. Understanding how assessors think—and practicing that mindset before they arrive—transforms the assessment from a stress test into a showcase of your cybersecurity culture. If you’re preparing for your first CMMC assessment, consider starting with a mock assessment. It’s the best way to see your program through the lens of C3PAO before it counts.

As a Registered Provider Organization, Planet has guided hundreds of organizations through the CMMC process. From rapid technology deployments and gap assessments of existing systems to compliance documentation and mock assessments, Planet is here to help. Contact us at [email protected] and start your CMMC journey with Planet today.