An Equilibrium Analysis of Optimal Audit Contracts

The nature of optimal equilibrium contracts for auditors hired by firms to certify the validity of firms' financial reports is studied in this paper. Financial reports may affect the interest rates at which firms can borrow funds; hence, without auditing, firms might be inclined to present favorable, if not altogether accurate, financial information. We observe that an optimal audit contract that allows auditors' contracts to be contingent on the audit report can take different forms depending on the parameter values; only in rare cases is an optimal contract independent of the audit report. Specifically, in some cases, an optimal contract is characterized by a payment for a favorable report that is larger than the payment for an unfavorable report. In other cases, the conclusion is reversed. We note, in contrast to the spirit of agency models, that an audit contract need not function in equilibrium as a motivational device inducing the auditor to work; in some cases, it serves as a means to transfer signaling costs from low-risk firms to high-risk firms. We also provide a rationale for mandating noncontingent audit contracts. In some circumstances equilibria in which auditing is informative cannot exist when contingent contracting is allowed; once contracts are required to be noncontingent, however, there exist equilibria in which auditing is informative.