Assurance service is an independent professional service, typically provided by Chartered or Certified Public Accountants or Chartered Certified Accountants, with the goal of improving information or the context of information so that decision makers can make more informed, and presumably better, decisions.
Consulting services are not considered as assurance[2] because in consulting services, an accountant generally uses their professional knowledge to make recommendations for a future event or a procedure, such as the design of an information system or accounting control system.
In contrast, assurance services are designed to test the validity of past data of the business cycles.
Although there is no boundary to what can be tested by assurance services, professional accountants cannot accept any engagement for which they do not believe themselves to be competent.
Technical guidance for practitioners wishing to undertake assurance services can be found in ISAE (International Standard on Assurance Engagements) 3000 ISAE 3000 and in The Assurance Sourcebook[5] published by ICAEW (Institute of Chartered Accountants in England and Wales) which also includes advice for companies wishing to choose between various assurance services.