Boundaries are ubiquitous in modern social life, and the work of creating and maintaining boundaries is particularly evident within regulatory fields. Through the analysis of a recent critical incident in the tax field (Arctic Systems) with which the accounting profession is intimately associated, this paper uses a Bourdieusian lens to unravel the relational complexities of the regulation of tax avoidance at the complex and fuzzy boundary between acceptable and unacceptable tax practice. We develop an alternative, relational interpretation of tax regulation and contribute to a more nuanced understanding of regulatory practice within the tax field that also raises questions about regulatory practice more widely We conclude by highlighting how a move towards ‘relational’ regulation might contribute to improved understanding of regulatory processes and practices