This paper argues that the Big Four accountancy firms—PricewaterhouseCoopers, Deloitte, Ernst & Young, KPMG—operate as key political allies of the financial sector within financial regulatory battles. Leveraging the theoretical notion of “actor plurality” within the policymaking process, I demonstrate how, in the case of the European Union Financial Transaction Tax (FTT) initiative, accountancy professionals offered crucial support for the financial sector. They did so by disseminating key oppositional claims against the FTT proposal, developing tax mitigation and relocation strategies, preparing negative impact assessments, and advising on lobbying tactics. This allied stance of the Big Four is primarily a consequence of the ways in which their commercial priorities have been fundamentally transformed by the provision of consultancy services within the modern global economy. Moreover, the paper shows how accountancy experts are deeply embedded within a network of professional relationships that fosters substantive policy alignment between the Big Four and prominent financial lobbying groups. By highlighting the overlooked role of the major accountancy firms within post crisis regulatory reform, the study illuminates the unequal power relations that permeate financialized societies and contributes to a deeper understanding of how financial preferences continue to prevail within the policymaking process.