CMMC Deadlines: What Defense Contractors Need to Know Before 2026

CMMC Deadlines Introduction

I am going to write a three-part blog post about the CMMC deadlines, the three levels of certification, and a step-by-step guide on how to become CMMC compliant. Please review all three posts and let me know if you require additional information about the CMMC deadlines or the process for becoming compliant.

The defense contracting landscape is transforming. As cyberattacks targeting defense contractors and subcontractors have grown, the Department of Defense has recognized that patchwork security measures are no longer sufficient to protect sensitive government information. The result is the Cybersecurity Maturity Model Certification, or CMMC—a comprehensive framework that is rapidly moving from optional guidance to mandatory requirement. The CMMC deadline is quickly approaching.

For the more than 300,000 companies that comprise the Defense Industrial Base, CMMC compliance represents both a challenge and an opportunity. It’s a challenge because achieving certification requires significant investment in cybersecurity infrastructure, documentation, and assessment processes. It’s an opportunity because contractors who achieve compliance early will find themselves well-positioned in a competitive marketplace where non-compliant businesses will be unable to bid on new contracts.

The urgency to become CMMC compliant cannot be overstated. With critical deadlines arriving in November 2026, defense contractors face a short timeline to assess their current security posture, identify gaps, implement necessary controls, and complete formal assessments. Businesses that delay action risk finding themselves scrambling to meet requirements at the last moment, potentially losing access to contracts that represent the lifeblood of their business. This article provides a comprehensive guide to understanding CMMC, navigating its requirements, and preparing for the CMMC deadlines that will reshape the defense contracting ecosystem.

What Is CMMC and Why Was It Created?

The Cybersecurity Maturity Model Certification represents the Department of Defense’s most ambitious effort to date in standardizing and enforcing cybersecurity practices across its entire supply chain. At its core, CMMC is a verification framework designed to ensure that every company handling sensitive government information has implemented appropriate cybersecurity controls for handling the sensitivity of that information.

CMMC emerged because breaches weren’t just affecting large contractors with complex security operations; they were occurring throughout the supply chain, often at smaller subcontractors who lacked the resources or expertise to implement cybersecurity controls. Each successful attack potentially compromised national security, giving attackers access to technical specifications, operational plans, and other information that could undermine U.S. defense capabilities.

The Defense Industrial Base encompasses a lot of organizations, ranging from multinational aerospace corporations to small machine shops that produce specialized components. With more than 300,000 direct and subcontracting participants, the DIB presents countless potential entry points for cybercriminals and nation-state actors seeking access to government information. CMMC addresses this challenge by establishing uniform standards that apply across the entire supply chain, eliminating the weakest links that adversaries have historically exploited.

The framework focuses on two categories of sensitive information: Federal Contract Information and Controlled Unclassified Information. Federal Contract Information includes data provided by or generated for the government under a contract that is not intended for public release. This may include bid or proposal information, financial data, or other contract-specific details. Controlled Unclassified Information represents a higher level of sensitivity and includes information that requires safeguarding or dissemination controls in accordance with laws, regulations, or government-wide policies. CUI might include technical specifications, engineering drawings, operational procedures, or other information whose unauthorized disclosure could harm national security interests.

Critical CMMC Deadlines

Phase 1: November 10, 2025 – Enforcement Begins

The first significant milestone in CMMC deadlines started on November 10, 2025, marking the beginning of active enforcement. Starting on this date, new Department of Defense solicitations and contracts will begin including CMMC requirements as mandatory contract terms. This timeframe represents a fundamental shift from the voluntary compliance environment that has characterized previous cybersecurity requirements to a regime where compliance is a threshold requirement for contract eligibility.

At this initial phase, contracts will require either Level 1 or Level 2 self-assessments depending on the information being handled. For many contractors, particularly those already familiar with NIST SP 800-171 requirements, the self-assessment process may seem straightforward. However, it’s important to recognize that even self-assessments must be thorough, accurate, and supported by evidence. The Department of Defense has made it clear that false certifications or misrepresentations in self-assessments can result in serious consequences, including contract termination, suspension, or debarment from future contracts, as well as potential liability under the False Claims Act.

For contractors actively pursuing new business, this deadline has immediate implications. Companies without completed self-assessments and proper documentation will be unable to compete for new contracts that include CMMC requirements. Even if a business has strong cybersecurity practices in place, without the formal assessment and documentation required by CMMC, it will be ineligible for contract award.

The November 2025 CMMC deadline also has implications beyond new contract awards. While existing contracts will continue under their current terms, companies should be aware that contract modifications or extensions may trigger new CMMC requirements. Additionally, contracts that don’t initially include CMMC requirements, as they were awarded before the deadline, may still require compliance if they’re extended or renewed after the deadline passes. Smart contractors are therefore planning for CMMC compliance not just for new business development but to protect their existing contract base.

Phase 2: November 10, 2026 – Third-Party Assessments Introduced

The second major milestone arrives exactly one year later, on November 10, 2026, when the most stringent CMMC deadline requirements take full effect. This date marks two critical changes: the introduction of mandatory third-party assessments for prioritized acquisitions at Level 2, and the full integration of CMMC requirements across all new defense contracts.

The requirement for third-party assessments represents a significant escalation in both the rigor and cost of compliance. Unlike self-assessments, which companies can conduct using internal resources, third-party assessments must be performed by Certified Third-Party Assessment Organizations that the CMMC Accreditation Body has authorized. These assessments are comprehensive, typically requiring several days or even weeks of intensive evaluation, depending on the scope and complexity of the systems being assessed. Assessors will review documentation, interview personnel, examine system configurations, and verify that security controls are not only implemented but are operating effectively.

Companies subject to prioritized acquisition requirements should begin planning for their C3PAO assessments well in advance of the November 2026 CMMC deadline. The number of authorized C3PAOs is limited, and as the deadline approaches, their schedules will fill rapidly. Contractors who wait until the last moment may find themselves unable to secure assessment slots in time to meet contract requirements. Additionally, the assessment process itself often identifies gaps or weaknesses that must be remediated, potentially requiring a follow-up assessment. Allowing sufficient time for both initial assessment and potential remediation is essential.

By November 2026, all new defense contracts will include CMMC requirements as standard terms. At this point, having a valid certification or self-assessment recorded in the Supplier Performance Risk System becomes a mandatory prerequisite for contract award. The SPRS serves as the authoritative repository of contractor cybersecurity information, and contracting officers will verify CMMC compliance status before making award decisions. Contractors without proper SPRS documentation will be passed over regardless of how competitive their technical proposals or pricing might be.

The planning timeline for meeting the November 2026 deadline is more compressed than many contractors realize. A typical timeline for a Level 2 third-party assessment might include three to six months for gap remediation after an initial readiness assessment, one to two months for documentation development, several weeks for scheduling and preparing for the actual assessment, and additional time for addressing any findings and completing follow-up verification. Organizations that haven’t begun their compliance journey by early 2025 may struggle to meet the deadline, particularly if they’re starting from a low baseline of cybersecurity maturity.

Full Operational Rollout: 2028

While the critical deadlines fall in 2025 and 2026, the full operational rollout of CMMC is expected to continue through 2028. By this point, CMMC will be fully integrated across all applicable defense contracts, with compliance serving as a standard requirement for doing business with the Department of Defense. The distinction between “new” contracts subject to CMMC and “existing” contracts without requirements will largely disappear as contracts come up for renewal or modification.

The 2028 target date for full implementation reflects the Department of Defense’s recognition that transforming cybersecurity practices across more than 300,000 businesses is a massive undertaking that cannot happen overnight. However, it would be a mistake for contractors to view 2028 as the “real” deadline and the earlier milestones as less critical. Companies that delay compliance until the absolute last moment will face several disadvantages: they’ll be competing for limited assessment resources when demand is highest, they’ll have less time to address unexpected complications or findings, and they’ll be entering a marketplace where competitors have already established their compliance credentials.

The framework will inevitably reshape the Defense Industrial Base, potentially consolidating work among larger contractors with established compliance programs, while creating barriers to entry for smaller companies lacking adequate cybersecurity resources. However, this transformation also creates opportunities for contractors who invest early in compliance to differentiate themselves and capture market share. The period between now and 2028 represents a window during which forward-thinking organizations can establish competitive advantages that will persist for years to come.

Why Work With Tanner Security Before the CMMC Deadline

CMMC compliance is not just a checkbox, it is an improvement process for how your company manages risk, data, and accountability. Tanner Security helps defense contractors avoid costly missteps, scope CUI correctly, and build compliance programs that can pass a CMMC audit.

Our team brings decades of experience in defense cybersecurity, NIST frameworks, and real-world assessment readiness. We help you meet deadlines confidently, without over-engineering or unnecessary cost. Contact us today to discuss your CMMC needs.