Evidence

In a CMMC context, evidence is documented proof that a specific NIST SP 800-171 requirement has been implemented and is operating in the contractor's environment. Evidence is what a C3PAO assessor actually looks at to make a met / not met / not applicable determination on an assessment objective.

Acceptable evidence types include policies, procedures, screenshots, configuration exports, training records, access reviews, vulnerability scan reports, incident response logs, change tickets, audit trails, and interview notes. The most defensible evidence is dated, attributable to a person, mapped to a specific assessment objective, and consistent with what other evidence in the assessment shows.

The most common assessment failure is not that requirements are unmet, but that the evidence demonstrating implementation is scattered, undated, or inconsistent. Organizing evidence by assessment objective from the start of the program — not the week before the assessment — is the single biggest determinant of a smooth Level 2 audit.