How many samples will an auditor actually pull, and can we influence it?

For SOC 2 and CMMC, auditors typically employ a risk-based sampling approach. Controls operating frequently, such as daily access reviews, generally necessitate a larger sample size than those performed less often, like quarterly vulnerability scans. The auditor evaluates the control's inherent risk, the effectiveness of the entity's general IT controls, and the quality and completeness of evidence provided. If evidence is incomplete, inconsistent, or challenging to obtain, auditors may expand their sample size to achieve sufficient assurance, potentially increasing audit effort and associated costs. Conversely, well-documented processes, clear evidence trails, and effective monitoring can significantly streamline the sampling process.

A common misconception is that a fixed percentage or number of samples applies universally across all audits or control types. This is incorrect; auditors exercise professional judgment guided by established auditing standards. Organisations frequently err by not maintaining comprehensive, readily accessible evidence for all control activities throughout the audit period. Attempting to influence sample size by withholding information or presenting curated data is counterproductive and can lead to adverse findings or an expanded audit scope. Instead, practitioners should focus on demonstrating a mature control environment, proactively providing complete and accurate evidence, and engaging transparently with the audit team to facilitate an efficient and effective assessment.