We focus on a relatively neglected area of the tax-compliance literature in economics, the behaviour of firms. We examine the impact of alternative audit rules on receipts from a tax on profits in the context of strategic inter-dependence of firms. In the market firms may compete in terms of either output or price. The enforcement policy can have an effect on firms’ behaviour in two dimensions - their market decisions as well as their compliance behaviour. An appropriate design of the enforcement policy can thus have a “double dividend” by manipulating firms in both dimensions.