Due to practical constraints, an audit seeks to provide only reasonable assurance that thestatements are free from material error. Hence, statistical sampling is often adopted in audits. In the case of financial audits, a set of financial statements are said to be true and fair when they are free of material misstatements - a concept influenced by both quantitative (numerical) and qualitative factors.
Auditing is a vital part of accounting. Traditionally, audits were mainly associatedwith gaining information about financial systems and the financial records of a company or a business (see financial audit). However, recent auditing has begun to include non-financial subject areas, such as safety, security, information systems performance, and environmental concerns. With nonprofit organizations and government agencies, there has been an increasing need for performance audits,examining their success in satisfying mission objectives. As a result, there are now audit professionals who specialize in security audits, information systems audits, and environmental audits.In cost accounting, it is a process for verifying the cost of manufacturing or producing of any article, on the basis of accounts measuring the use of material, labour or other items of cost. In simple wordsthe term, cost audit, means a systematic and accurate verification of the cost accounts and records, and checking for adherence to the cost accounting objectives. According to the Institute of Cost and Management Accountants of Pakistan, a cost audit is "an examination of cost accounting records and verification of facts to ascertain that the cost of the product has been arrived at, in accordancewith principles of cost accounting."
An audit must adhere to generally accepted standards established by governing bodies. These standards assure third parties or external users that they can rely upon the auditor's opinion on the fairness of financial statements, or other subjects on which the auditor expresses an opinion.
The Definition for Auditing and Assurance Standard (AAS) 1 by ICAI- "Auditing is the independent examination of financial information of any entity, whether profit oriented or not, and irrespective of its size or legal form, when such an examination is conducted with a view to expressing an opinion thereon."
 Integrated audits
In the US, audits of publicly traded companies are governed by rules laid down by the Public Company Accounting OversightBoard (PCAOB), which was established by Section 404 of the Sarbanes-Oxley Act of 2002. Such an audit is called an integrated audit, where auditors, in addition to an opinion on the financial statements, must also express an opinion on the effectiveness of a company's internal control over financial reporting, in accordance with PCAOB Auditing Standard No. 5.
There are also new types of integratedauditing becoming available that use unified compliance material (see the unified compliance section in Regulatory compliance). Due to the increasing number of regulations and need for operational transparency, organizations are adopting risk-based audits that can cover multiple regulations and standards from a single audit event. This is a very new but necessary approach insome sectors to ensure that all the necessary governance requirements can be met without duplicating effort from both audit and audit hosting resources.
The purpose of an assessment is to measure something or calculate a value for it. Although the process producing an assessment may involve an audit by an independent professional, its purpose is to provide a...