Definicija: služba, oddelek ..., ki jo vzpostavi organizacija sama v okviru pristojnosti svoje najvišje hierarhične ravni. Njene funkcije so med drugim preverjanje, vrednotenje ter spremljanje ustreznosti in učinkovitosti ureditve računovodstva, notranjega kontroliranja, preprečevanje prevar in korupcije ter pridobivanja zagotovila, da procesi delujejo v skladu s temi načeli. Čeprav ima večino enakih značilnosti kot zunanja revizija, pa praviloma deluje po usmeritvah vodstva, kateremu poroča.

Definicija: The functional means by which the managers of an entity receive an assurance from internal sources that the processes for which they are accountable are operating in a manner which will minimise the probability of the occurrence of fraud, error or inefficient and uneconomic practices. It has many of the characteristics of external audit but may properly carry out the directions of the level of management to which it reports.