Voluntary vs. mandatory: the role of auditing in constraining corporate tax avoidance in small private firms

This paper examines whether the status of the financial statement audit, as either voluntary or mandatory, is related to the corporate tax avoidance behaviour of private firms. Using the Swedish audit regime shift in 2010 which removed mandatory audit requirements for small private companies, we find that voluntarily audited firms exhibit a 19% decrease in total income tax burden relative to firms subject to mandatory audit following the regulatory change. This decrease corresponds to an average SEK 15,000 (approximately 1,500 euros) lower tax payment and is driven primarily by increasing conforming tax avoidance. We also find that increasing tax avoidance in voluntarily audited firms occurs, at least partly, due to impaired auditor independence under the voluntary audit regime. Finally, we show that the non-tax costs of tax avoidance restrict these tax-driven reporting changes. Our findings contribute to the literature on auditors’ constraining effect on corporate tax avoidance as well as to the debate over the costs and benefits of a mandatory financial statement audit regime.