An auditor's report is a formal opinion, or disclaimer thereof, issued by either an internal auditor or an independent external auditor as a result of an internal or external audit, as an assurance service in order for the user to make decisions based on the results of the audit.

Auditor's reports are considered essential tools when reporting financial information to users, particularly in business. Many third-party users prefer, or even require financial information to be certified by an independent external auditor. Audit reports derive value from increasing the credibility of financial statements, which subsequently increases investors' reliance on them. In the government, legislative and anti-corruption entities use audit reports to keep track of the actions of public administrators on behalf of citizens. Therefore auditing reports are a check mechanism on behalf of the citizen, to ensure that public finances, resources and trust are managed in entities created to foster good governance, such as local authorities, government departments, ministries and related government bodies.

It is important to note that auditor reports on financial statements are neither evaluations nor any other similar determination used to evaluate entities in order to make a decision. The report is only an opinion on whether the information presented is correct and free from material misstatements, whereas all other determinations are left for the user to decide.

There are four common types of auditor's reports, each one presenting a different situation encountered during the auditor's work. The four reports are as follows:

An opinion is said to be unqualified when he or she does not have any significant reservation in respect of matters contained in the Financial Statements. The most frequent type of report is referred to as the "Unqualified Opinion", and is regarded by many as the equivalent of a "clean bill of health" to a patient, which has led many to call it the "Clean Opinion", but in reality it is not a clean bill of health, because the Auditor can only provide reasonable assurance regarding the Financial Statements, not the health of the company itself, or the integrity of company records not part of the foundation of the Financial Statements. This type of report is issued by an auditor when the financial statements are free of material misstatements and are presented fairly in accordance with the Generally Accepted Accounting Principles (GAAP), which in other words means that the company's financial condition, position, and operations are fairly presented in the financial statements. It is the best type of report an auditee may receive from an external auditor.

An Unqualified Opinion indicates the following –

(1) The Financial Statements have been prepared using the Generally Accepted Accounting Principles which have been consistently applied;

(2) The Financial Statements comply with relevant statutory requirements and regulations;