An auditor is a professional who examines an organization’s financial records, operations, and internal controls to verify accuracy and compliance with laws or standards. Auditors work across industries, from major accounting firms reviewing public companies to in-house teams evaluating how efficiently a business runs. Their core job is to provide an independent, objective assessment of whether the numbers add up and whether the organization is following the rules.
What an Auditor Actually Does
At the most basic level, auditors track money from beginning to end. They inspect accounting data, financial records, and operational processes, taking detailed notes at each step to create what’s called an audit trail: a documented chain of evidence showing how they reached their conclusions.
For public companies, the central task is determining whether financial statements follow generally accepted accounting principles (GAAP), the standardized rules that govern how companies report their finances. But the work goes well beyond checking math. Auditors assess risk management practices, test internal controls (the safeguards a company uses to prevent errors or fraud), evaluate whether cash flow is properly accounted for, and look for discrepancies that could signal anything from sloppy bookkeeping to deliberate fraud.
Once the examination is complete, the auditor produces a formal report. For external audits of public companies, this report appears alongside the company’s financial statements and gives investors and regulators an independent opinion on whether those statements are reliable. Separate, private reports may also go to company management or regulatory authorities with more specific findings.
Three Main Types of Auditors
Internal Auditors
Internal auditors work inside an organization as employees, but they operate independently from the departments they review. Their job is to evaluate both financial and operational activities, including corporate governance (how well leadership oversees the company). They report their findings to senior management, often with recommendations on how to improve efficiency, reduce risk, or strengthen controls. Internal auditors serve as an early warning system, catching problems before they become public crises.
External Auditors
External auditors are independent professionals, typically from accounting firms, hired to provide an outside opinion on a company’s financial statements. Their role is public-facing: they assess whether financial reports fairly and accurately represent the organization’s financial position. This independence is the whole point. Investors, lenders, and regulators rely on external auditors precisely because they have no loyalty to the company they’re examining.
Public companies listed on U.S. stock exchanges are required by the Securities and Exchange Commission to undergo annual external audits. Insured banks and other depository institutions with total assets of $500 million or more must also have independent audits under federal banking law. Many private companies face audit requirements too, depending on their size, industry, or loan covenants with banks.
Government Auditors
Government auditors work for federal, state, or local agencies. They examine the records of government bodies and private businesses subject to government regulations or taxation. Their focus is ensuring that public revenues are collected and spent according to the law. They also detect embezzlement and fraud, analyze agency accounting controls, and evaluate risk management within government operations.
Education and Certification
Most auditing positions require at least a bachelor’s degree in accounting, finance, or a related field. Beyond that, professional certifications distinguish auditors and often determine what kinds of work they’re qualified to perform.
The CPA (Certified Public Accountant) is the standard credential for external auditors. Only licensed CPAs can sign off on the audited financial statements of public companies. Earning a CPA requires passing a four-part exam, meeting state-specific education requirements (typically 150 college credit hours), and completing supervised work experience.
The CIA (Certified Internal Auditor) is the primary credential for internal auditors, issued by the Institute of Internal Auditors. Candidates must pass a three-part exam: Part 1 has 125 questions over 2.5 hours, and Parts 2 and 3 each have 100 questions over 2 hours. You have three years from acceptance into the program to complete all parts. Experience requirements depend on your education level: one year of internal audit experience with a master’s degree, two years with a bachelor’s degree, or five years if you hold an Internal Audit Practitioner certification instead of a traditional degree. If you already hold an active CPA or CA (Chartered Accountant) license, the education requirements are waived, and you can take a condensed challenge exam instead of the full three parts.
The CISA (Certified Information Systems Auditor) focuses on IT auditing, covering cybersecurity controls, data integrity, and technology governance. Active CISA holders can also qualify for the CIA challenge exam pathway.
What Triggers a Required Audit
Not every business needs a formal audit. The requirement typically kicks in based on company size, public listing status, or regulatory oversight. All publicly traded companies in the U.S. must have their financial statements audited annually. Nonprofit organizations frequently face audit requirements once they receive a certain level of federal funding. Banks, insurance companies, and other regulated financial institutions have their own thresholds set by federal and state regulators.
Private companies may need audits if their lending agreements require them, if they’re preparing for an acquisition, or if they plan to go public. Some states also require audited financials from businesses above certain revenue levels. Even when not legally required, many mid-size companies voluntarily undergo audits to build credibility with investors, lenders, or potential buyers.
How Technology Is Changing the Work
Auditing has traditionally relied on sampling, where auditors review a subset of transactions and use that sample to draw conclusions about the whole. AI-powered audit analytics platforms now allow auditors to analyze entire datasets rather than small samples. Tools like MindBridge use artificial intelligence to identify unusual transactions, detect fraud patterns, and flag anomalies across millions of records that a human reviewer would never catch through manual testing.
This shift doesn’t replace auditors, but it changes what they spend their time on. Less time goes to manually pulling and cross-referencing records, and more goes to investigating the outliers that automated analysis surfaces, exercising professional judgment about what those anomalies mean, and communicating findings to stakeholders. The core skill set is evolving: today’s auditors increasingly need comfort with data analytics alongside their accounting expertise.
Where Auditors Work and What They Earn
External auditors typically work at public accounting firms, ranging from the Big Four (Deloitte, PricewaterhouseCoopers, EY, and KPMG) to regional and local practices. Internal auditors are employed directly by corporations, hospitals, universities, and other large organizations. Government auditors work for agencies like the Government Accountability Office at the federal level, or for state audit offices and inspectors general.
Entry-level auditors at accounting firms generally start in the $55,000 to $75,000 range, depending on location and firm size. Senior auditors and audit managers earn significantly more, and partners at major firms can earn well into six figures. Internal auditors at large corporations often command competitive salaries with more predictable hours than their public accounting counterparts, who face intense workloads during busy season (typically January through April).
Career progression in external audit usually follows a structured path from staff auditor to senior, then manager, senior manager, and eventually partner. Internal auditors may advance to chief audit executive or transition into broader risk management and compliance leadership roles. The analytical and investigative skills auditors develop also translate well into corporate finance, consulting, and executive management positions.