A survey of models for determining optimal audit strategies

The problem studied in this survey is how to optimize the allocation of audit resources over an auditee population with respect to available population statistics. The auditees are assumed to optimize their expected utility based on information about the audit strategy. This survey is limited to models where the auditee can vary the fraud amount along a continuous scale.If the auditor is not able or willing to announce the audit strategy, a Nash equilibrium can be derived in which the auditor and auditee correctly anticipate each other's strategies. If the auditor announces the audit strategy in advance, the problem is formulated as a sequential game with perfect information which is solved as an optimization problem.Early models in the literature resulted in unrealistically high degrees of fraud. Later models have incorporated a split into one group of inherently honest auditees and another group of potentially dishonest auditees. The fraction of inherently honest auditees is exogenous.In this paper, the four combinations of non-announcing/pre-announcing the strategy and all potentially dishonest/some inherently honest auditees are studied. For the case of pre-announcing the strategy with some inherently honest auditees, two new solution methods are presented.Two main conclusions are as follows. First, models with some inherently honest auditees have greater external validity. Second, when a pre-announced strategy is feasible, as it often is with tax and benefit audits, the pre-announced strategy is preferred by the auditor over the non-announced strategy.