For many leaders in the Defense Industrial Base, CMMC feels like a maze of rules, consultants, and acronyms. It’s easy to believe that once you hire the right MSP, consultant, or enclave provider, your compliance challenges are behind you. But CMMC doesn’t work that way.

Compliance isn’t something you can buy—it’s something your organization builds.

That’s where the Shared Responsibility Matrix (SRM) comes in. This document maps out which controls are owned by your organization (the OSC) and which are handled, or supported, by external service providers. Understanding and accurately defining those responsibilities is one of the most important steps you can take to prepare for assessment. It is also an important part of understanding inheritance and building your System Security Plan that you will need for your assessment.

How the C3PAO Uses Your Shared Responsibility Matrix

When a C3PAO assessor reviews your environment, one of the first things they’ll look for is evidence that your organization understands its responsibilities as they relate to the tools and services provider that you use. The SRM serves as part that roadmap.

Assessors use the matrix to confirm:

• Which entities (internal or external) are performing specific control activities.
• Where evidence should come from (your organization or your providers).
• Whether any responsibilities are unclear or missing.

If your SRM is vague, incomplete, or doesn’t reflect how your environment truly operates, it becomes immediately apparent during the assessment. We’ve seen companies list a single provider as responsible for “security,” but in reality they had three: a managed IT provider, a cloud hosting provider, and an enclave vendor. Each of those relationships carries its own compliance implications.

A well-constructed SRM clearly identifies each provider, the controls they support, and most importantly, what remains under the OSC’s ownership.

Multiple Providers, Shared Accountability

In today’s environments, it’s rare for one company to handle everything. You may have one MSP managing your network, another provider your enclave or cloud applications, and a separate consultant guiding your CMMC readiness activities. Each plays an important role, but none can replace the organizational leadership decisions that belong to you.

For example:

• Your MSP can configure MFA and manage user accounts, but you decide who’s authorized to have access.
• Your enclave provider can maintain a secure environment, but you determine what data belongs there and who’s responsible for uploading it.
• Your consultant can help document your System Security Plan, but you sign off on policies and risk acceptance.

An accurate SRM ensures everyone understands their role, so nothing “falls between the cracks.” During an assessment, that clarity prevents delays, finger-pointing, and confusion.

The Leadership Connection

As a leader, your job isn’t to master every technical control, it’s to understand how responsibilities flows through your organization and the ones you interact with.

The SRM is a leadership tool, not just a compliance document. It helps you see:

• Who holds decision-making authority over key systems.
• Where organizational accountability stops and vendor accountability begins.
• Whether your contracts, SLAs, and evidence align with those assignments.

When your C3PAO reviews your SRM, they’re not only looking for completion- they’re looking for understanding. A strong matrix tells us that your organization has internalized the shared model and can articulate how you manage risk across partnerships.

That confidence is a marker of maturity, and it often separates companies that are ready from those that are just documented.

Building Compliance That Lasts

Compliance is built on collaboration- but it starts with ownership.

Your partners can configure systems, provide secure hosting, and help guide your documentation, but they can’t decide your policies or your level of risk tolerance. The SRM brings all these moving parts together into one clear, actionable picture.

So, as you prepare for your assessment, take the time to ensure your SRM actually reflects how your environment operates. Name your providers, describe their roles, and make sure everyone, from IT to HR to leadership, knows what belongs to the OSC.

Because when the C3PAO walks in, the first question isn’t “Who’s responsible?” it’s “Do you know who’s responsible?”

And the organizations that can confidently answer that question are the ones that lead their organization from a place of informed strength.

Reach out to us today if you have questions.