Using The Work Of Others — Evaluate Use Of Specialists And Internal Audit

Historical Context & Motivation

The modern audit engagement is far too complex for a single generalist to handle alone. Financial statements routinely contain assertions about fair values of derivatives, actuarial liabilities, environmental remediation costs, and information-technology controls—areas where the external auditor's own expertise may be insufficient. Recognizing this reality, the auditing profession has long permitted, and in many cases encouraged, auditors to draw upon the work of auditor's specialists, management's specialists, and the entity's own internal audit function. The challenge lies not in whether to use such work, but in how to evaluate it, maintain professional skepticism, and preserve the external auditor's ultimate responsibility for the audit opinion.

The central question these standards address is straightforward yet nuanced: How does the external auditor use and evaluate the work of others without improperly delegating professional responsibility? The answer requires a disciplined framework of competence assessment, objectivity evaluation, testing of underlying data, and careful consideration of scope—topics we will explore throughout this lesson.

Core Principles & Definitions

Before examining the detailed procedures, it is essential to establish the foundational definitions and principles that govern how the external auditor interacts with specialists and internal audit. The standards draw sharp distinctions between parties based on who engaged them and what role they play relative to the financial statements and the audit.

Visual Framework — The Auditor's Decision Tree

The following diagram illustrates the external auditor's decision process when determining whether and how to use the work of others. The flowchart highlights the key evaluation gates—competence, objectivity, adequacy of work, and the nature of the area being audited—that the auditor must pass through before placing reliance on another party's work.

As depicted in the diagram, the auditor's first decision is whether the area of expertise calls for a specialist (such as a valuation expert or actuary) or whether internal audit has already performed relevant work. For specialists, the auditor must further distinguish between one engaged by the auditor (governed by AU-C 620) and one engaged by management (evaluated under AU-C 500). For internal audit, the critical consideration is whether the area involves significant judgments—if it does, the external auditor must re-perform the work rather than simply rely on internal audit's conclusions.

Detailed Evaluation Mechanisms

Evaluating an Auditor's Specialist (AU-C 620 / AS 1210)

When an external auditor engages a specialist—for example, a valuation analyst to appraise a portfolio of complex financial instruments—the auditor must perform a structured evaluation before placing any reliance on the specialist's findings. The evaluation proceeds along three dimensions: competence, objectivity, and adequacy of work performed. Competence is assessed through credentials (e.g., ASA designation for appraisers, FSA for actuaries), relevant experience, professional reputation, and standing in peer organizations. Objectivity analysis examines whether the specialist has financial interests in the client, family or business relationships with client management, or other conflicts that might bias their conclusions. Even if the specialist is engaged by the audit firm itself, objectivity threats can arise if the specialist simultaneously provides advisory services to the audit client.

The auditor must reach an understanding with the specialist regarding the nature, scope, and objectives of the work; the respective roles and responsibilities; the methods and assumptions to be used; and the form of the specialist's report. This understanding is typically documented in an engagement letter or memorandum. The auditor then evaluates the specialist's findings by assessing the relevance and reasonableness of the assumptions, the completeness of the source data, and the internal consistency of the specialist's report. Importantly, the auditor need not possess the same technical expertise as the specialist, but must have sufficient understanding to evaluate whether the work provides appropriate audit evidence.

Evaluating Management's Specialist (AU-C 500)

When management uses a specialist to prepare financial statement amounts—consider a pension actuary computing the projected benefit obligation—the auditor treats the specialist's output as part of management's assertions. The evaluation framework under AU-C 500 mirrors the specialist evaluation above but adds an important layer: the auditor must test the underlying data that management provided to the specialist and evaluate the reasonableness of significant assumptions. For instance, if the actuary used employee census data, the auditor should vouch a sample of that data back to HR records. If the actuary assumed a 7% discount rate, the auditor should evaluate whether that rate is consistent with current market conditions and industry norms.

Evaluating the Internal Audit Function (AU-C 610 / AS 2605)

The external auditor may use the internal audit function in two distinct ways: (1) using internal audit's work as audit evidence and (2) using internal auditors to provide direct assistance under the external auditor's supervision. In either case, the external auditor must evaluate the internal audit function's organizational status (reporting line to the audit committee rather than to operating management), competence (professional certifications such as CIA, adequate staffing, continuing education), and whether their work is performed with due professional care (adequate planning, supervision, documentation, and review). A critical constraint is that the external auditor cannot use internal audit work—or direct assistance—in areas requiring significant auditor judgment, such as assessing accounting estimates or evaluating the adequacy of disclosures. For PCAOB engagements (issuers), the standard is even more restrictive: internal auditors cannot serve as direct assistants.

Classification of Work-of-Others Relationships

Understanding the distinctions among the various parties whose work the external auditor may consider is critical for exam success. The following table provides a side-by-side classification, and the diagram below maps these relationships visually to show how information flows between the parties and the external auditor.

Worked Example — Evaluating Use of a Specialist and Internal Audit

Consider the following scenario: you are the senior auditor on the engagement for Apex Manufacturing, Inc. Apex has a defined-benefit pension plan. Management engaged an actuary (Smith & Associates) to compute the projected benefit obligation (PBO). Additionally, Apex's internal audit department performed testing of the payroll controls that feed employee census data to the actuary. You need to determine how to evaluate and use both sources of work.

Strengths, Limitations, and Common Pitfalls

Using the work of others provides significant benefits in terms of audit efficiency and evidence quality, but also introduces risks that the external auditor must manage carefully. The following table summarizes the key strengths and limitations, followed by common exam pitfalls that CPA candidates should be aware of.

Connection to Advanced Audit Topics

The principles governing the use of specialists and internal audit connect directly to broader audit theory and advanced engagement scenarios. Understanding these connections is important both for the CPA exam and for practice. The evaluation of specialists plays a critical role in auditing accounting estimates (AU-C 540), which are among the most judgment-intensive areas of any audit. When fair value measurements involve Level 3 inputs under ASC 820, the auditor almost invariably needs specialist assistance to evaluate management's models and assumptions.

As you advance through the AUD section, you will encounter these concepts repeatedly. The ability to recognize when a scenario involves a specialist versus internal audit, to recall the correct governing standard, and to apply the appropriate evaluation framework will be tested in both multiple-choice and task-based simulation formats. Pay particular attention to the interplay between specialist reliance and the audit risk model—using a well-qualified specialist effectively reduces detection risk for the assertions the specialist's work addresses, whereas an inadequate evaluation of a specialist may increase audit risk by introducing unreliable evidence into the auditor's conclusion.

Practice Problems

Lesson Summary