Assurance services are a class of services provided by certified public accountants (CPAs) in public practice. While the term is sometimes used inconsistently among individual CPA firms, the American Institute of Certified Public Accountants (AICPA) Special Committee on Assurance Services defined assurance services as "independent professional services that improve the quality of information, or its context, for decision-makers."

Assurance services are rooted in the CPA's tradition of independent verification of data prepared by others. They differ from many services historically provided by CPAs in that they represent an expansion of the information and forms of reports provided. Indeed, they represent an evolution in the nature of services provided by CPAs, as CPAs have begun to provide services not just on accounting information but on many other types of information that people need in order to make decisions.

The Evolution of Cpa Services

Since the early part...