What produces the power of senior civil servants at ministries of finance, positioned at the top of the bureaucratic hierarchy? Max Weber has claimed that a hierarchical organization, meritocratic recruitment and procedural work provide bureaucracies with legitimacy. In particular he insisted on the role of Fachwissen (disciplinary knowledge) obtained through formal education. However, he also argued for the role of Dienstwissen, forms of knowledge and skills stemming from the experience of service in itself. Weber did not elaborate on this concept in detail, and few analysts of governmental expertise have examined this notion. We draw on the practice‐turn in sociology, combining the study of governmental expertise with micro‐sociological studies of administrative practices. By analysing interviews with 48 senior civil servants at the British, French and Norwegian ministries of finance about their daily practices, this article demonstrates that bureaucratic note‐writing and the procedural evaluation of such notes constitute a key form of expertise that yields authority. The study provides an analytical framework for understanding what administrative expertise consists of, how it is integral to procedural work, the forms bureaucratic hierarchies take in practice and how these three dimensions provide authority.