What Is an Audit? Meaning, Types and Importance

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An audit is an independent, evidence-based examination of an organization’s financial records and statements, carried out by qualified professionals, to determine whether those statements are presented fairly, in all material respects, under the applicable accounting framework. In plain terms, an auditor checks whether the numbers a company reports can be trusted. The financial statements remain management’s responsibility. The auditor’s job is to test them and issue an opinion that investors, lenders, regulators and the public can rely on.

Auditing covers the main financial statements: the balance sheet, the income statement and the cash flow statement, along with the notes that explain them. Depending on the engagement, it can also cover internal controls, tax filings or compliance with specific rules.

What does “audited” mean?

When financial statements are described as audited, an independent auditor has gathered enough evidence to express an opinion on them and has signed an audit report. “Audited financials” therefore carry more weight than statements management prepared on its own.

Two other services are often confused with an audit:

• Review: the accountant performs mainly inquiry and analytical procedures and provides limited assurance. U.S. public companies have their quarterly financial statements reviewed rather than audited.
• Compilation: the accountant helps present management’s information in financial statement form and provides no assurance.

Types of audits

External audits

An external audit is performed by independent certified public accountants who are not employees of the organization. They examine the financial records, test internal controls and gather enough evidence to conclude whether the statements are free from material misstatement, whether caused by error or fraud.

Independence is what gives the opinion its value: external auditors must have no financial interest or management role in the company they audit. Public companies in the U.S. must have their annual financial statements audited by an independent registered firm, and many private companies obtain audits because lenders, investors or regulators require them.

Internal audits

Internal audits are performed by the organization’s own employees, usually an internal audit department that reports to the board’s audit committee. Their focus is wider than the financial statements: they evaluate whether internal controls work, how risks are managed and whether staff follow policies, aiming to find weaknesses before small control failures become large losses or reporting problems.

Because internal auditors work for the company, their findings do not replace an external audit opinion, though external auditors may consider internal audit work when planning their own procedures.

Operational and compliance audits

• An operational audit evaluates how efficiently and effectively a process or department uses its resources. It might ask whether the purchasing function pays too much for supplies or whether warehouse procedures cause avoidable losses. It ends with recommendations, not an opinion on financial statements.
• A compliance audit checks whether the organization follows specific laws, contracts, grant terms or internal policies.

An external financial audit asks a narrower question: are the financial statements fairly presented? A company can receive a clean financial audit opinion and still have inefficient operations.

IRS audits

An IRS audit is an examination by the Internal Revenue Service of a tax return filed by an individual or organization, to verify that income, deductions and credits were reported correctly. Unlike the other types, it is initiated by the government, not requested by the company or its owners.

The IRS may select a return because of discrepancies in reported income, unusually large deductions or figures that differ statistically from similar taxpayers. Many audits are handled by mail when the issue is simple; more complex cases can involve in-person meetings with an IRS examiner. Taxpayers are expected to keep records that substantiate what they reported. An unfavorable result can lead to additional tax, penalties and interest. Being audited by the IRS does not by itself mean the taxpayer did something wrong; it means the return is being examined.

Standards that govern auditing

Auditors follow published standards covering ethics, how evidence is gathered and how findings are reported. Three frameworks dominate.

Generally Accepted Auditing Standards (GAAS)

GAAS, developed by the American Institute of Certified Public Accountants (AICPA), govern audits of U.S. private companies and other entities that are not public companies. They address the auditor’s competence and due care, the planning and evidence-gathering work (fieldwork) and how conclusions are communicated in the report.

Public Company Accounting Oversight Board (PCAOB)

The PCAOB was created by the Sarbanes-Oxley Act of 2002, passed after accounting scandals at Enron and WorldCom. It sets auditing standards for public companies whose securities trade in the U.S., registers the firms that audit them and inspects those firms for compliance. Its standards emphasize testing internal control over financial reporting, documentation and high-risk areas. Under Sarbanes-Oxley, management of a public company must assess that control, and for larger companies the auditor must also report on it.

International Standards on Auditing (ISA)

The ISA are issued by the International Auditing and Assurance Standards Board (IAASB) and have been adopted as national standards in many countries outside the U.S. They give multinational companies and international investors a common basis for comparing audits across borders.

How an audit works

Planning

The auditor first learns the business: its industry, its systems, its key accounting estimates and where the statements could go wrong. From this comes a risk assessment and a materiality threshold, the size of misstatement that could change the decisions of a reasonable user of the statements. Accounts with higher risk or larger balances get more testing.

Fieldwork

The auditor then gathers evidence, typically through:

• Examining and verifying documents such as invoices, contracts and bank statements
• Interviewing key personnel
• Analytical procedures that compare figures across periods or against expectations to spot unusual movements
• Substantive testing of selected account balances and transactions
• Evaluating accounting policies and management’s estimates

Most testing relies on sampling: the auditor selects a portion of transactions, examines them and draws conclusions about the whole population. Throughout, the auditor is expected to apply professional skepticism, keep detailed working papers that support each conclusion and remain independent.

Reporting

At the end, the auditor evaluates the evidence and forms an opinion. Misstatements found during the work are discussed with management, which can correct them. Significant findings, including control weaknesses, are communicated to management and those charged with governance, often in a management letter. The final product is the audit report, which states the auditor’s opinion and is published alongside the financial statements.

Interpreting the audit opinion

A clean opinion is the expected result for most well-run companies, which is why a qualified opinion, an adverse opinion or a disclaimer draws attention from investors and lenders. Readers should also look for an explanatory paragraph about going concern, which signals substantial doubt about the company’s ability to continue operating, even when the opinion itself is unqualified.

When audits happen

An external financial audit covers a fiscal year, so its timing follows the company’s year-end, not a fixed calendar month. A company with a December 31 year-end typically has planning and some interim testing during the year, then most of the year-end work in the following weeks. U.S. public companies must file their annual report on Form 10-K, including the audited statements, within 60, 75 or 90 days of year-end depending on their filer category. Each fiscal quarter in between, their interim statements are reviewed, not audited.

Internal audits run on their own schedule, usually set by an annual plan approved by the audit committee. IRS audits happen whenever a return is selected, often a year or more after filing.

Example of an audit

Hypothetical example for illustration only. Rivera Tools, a private manufacturer, needs audited statements to renew a bank loan. Its draft income statement shows $50 million of revenue and $4 million of pretax income.

1. Planning: The auditor sets overall materiality at $200,000 for this engagement and identifies revenue cutoff as a high-risk area, because the company ships a large volume of orders in the last week of December.
2. Fieldwork: The auditor selects a sample of sales recorded in late December and early January and matches each one to shipping documents. Several December sales turn out to have shipped in January. Projected across the population, the error suggests about $350,000 of revenue was recorded in the wrong year.
3. Resolution: Because $350,000 exceeds materiality, the auditor asks management to correct it. If management books the adjustment, revenue and receivables fall, and the auditor can issue an unqualified opinion. If management refuses, the auditor would consider a qualified opinion, since the problem is material but confined to one area.
4. Reporting: Whatever the opinion, the auditor tells the board that shipping and billing are not coordinated at year-end, and recommends a control to fix it.

Limitations of an audit

Reasonable, not absolute, assurance. An audit is designed to detect material misstatements, not every error. Because auditors sample transactions, a misstatement can go undetected, particularly one concealed by collusion or forged documents.

Judgment and estimates. Many balances, such as inventory reserves, asset impairments or warranty liabilities, depend on management’s estimates. The auditor evaluates whether they are reasonable, but reasonable estimates can still prove wrong.

Point in time. An opinion covers the statements for a specific period. It says nothing about how the company has performed since, or whether its strategy is sound. A clean opinion is not an investment recommendation.

Cost and disruption. Audits take significant staff time and fees, which can be large relative to a smaller organization’s resources.

A related misconception is that audits happen only when wrongdoing is suspected. External audits are routine, recurring engagements. Investigations aimed at suspected fraud are a separate discipline, forensic accounting.

FAQs

The Bottom Line

Audits matter to investors, lenders, regulators and business owners who rely on reported numbers to make decisions. A clean opinion means the statements are fairly presented, but it offers reasonable assurance, covers a specific period and is not an investment recommendation. Readers should check the opinion type, watch for going concern language and remember that an IRS examination of a tax return is a separate process.