What is a Service Auditor?

What is a Service Auditor?

A service auditor is a licensed CPA (Certified Public Accountant) firm that performs attestation engagements, including SOC 1, SOC 2, and SOC 3 examinations, on behalf of service organizations. The auditor independently evaluates whether an organization's controls meet the applicable criteria and issues a formal report with their professional opinion.

Role of the service auditor

The service auditor's primary responsibilities include:

• Evaluating control design — determining whether controls are suitably designed to meet Trust Services Criteria or other applicable standards
• Testing operating effectiveness — for Type II engagements, testing whether controls operated effectively over the observation period
• Issuing the audit report — providing a formal opinion on the organization's controls, including any exceptions identified
• Maintaining independence — the auditor must remain independent from the organization being audited to ensure objectivity

Qualifications and standards

Service auditors must be licensed CPA firms. They perform SOC engagements under professional standards including:

• SSAE 18 (Statement on Standards for Attestation Engagements No. 18) — the overarching attestation standard in the United States
• AT-C Section 205 — the specific standard governing examination engagements
• AICPA professional standards — including ethical requirements, quality control, and continuing education

Not all CPA firms perform SOC audits. Firms that specialize in SOC engagements typically have dedicated information security audit teams with relevant technical expertise.

Selecting a service auditor

Choosing the right auditor impacts the quality and efficiency of your audit. Consider:

• Experience — how many SOC 2 audits the firm performs annually, particularly in your industry
• Technical expertise — whether the audit team understands modern cloud infrastructure, SaaS architectures, and security tooling
• Communication style — whether the firm is collaborative and responsive, or rigid and difficult to work with
• Pricing and timeline — costs can vary significantly between firms, as can expected timelines
• Reputation — whether the firm's reports are recognized and accepted by your customers and prospects

What to expect during the audit

A typical SOC 2 audit engagement includes several phases:

1. Planning — the auditor defines scope, identifies key controls, and establishes the testing approach
2. Fieldwork — the auditor requests and reviews evidence, conducts interviews, and performs testing procedures
3. Draft review — the auditor shares a draft report for the organization to review for factual accuracy
4. Final report — the auditor issues the final report with their opinion

During fieldwork, the auditor may request documentation such as policies, screenshots, system configurations, access logs, and change records. Prompt and organized responses to these requests significantly reduce audit duration.

Auditor independence

Independence is a foundational requirement. The auditor cannot provide the consulting services that design the controls they will later audit. Some firms offer readiness assessments through separate teams to maintain independence boundaries, but organizations should confirm the firm's independence policies before engaging.

Common challenges

Organizations often face friction during audits due to:

• Incomplete or disorganized evidence
• Controls that exist in policy but are not consistently executed
• Misalignment between the system description and actual practices
• Delayed responses to auditor requests

Preparing thoroughly and maintaining organized evidence throughout the year minimizes these issues.

How episki helps

episki organizes your controls and evidence in a structured format that aligns with auditor expectations. The auditor portal provides secure, read-only access so your auditor can review evidence independently, reducing back-and-forth and shortening the fieldwork phase. Learn more on our SOC 2 compliance page.