Society’s efforts to ‘manage’ the problem of human-induced climate change – for example through setting targets, tracking progress, imposing sanctions and incentives, and creating markets in emission rights and offsets – have given rise to numerous calculation, measurement, attribution, monitoring, reporting and verification challenges, which are being addressed by many different communities (including scientists, governments, businesses and accountants) in many different ways. Carbon accounting – this diverse and ever-expanding assemblage of calculative practices – is a rapidly evolving phenomenon, which has only recently become a subject of academic accountancy-related research. This thesis explores what carbon accounting means, who it involves, and how different communities define and lay claim to competence in the field. It also examines, through case studies on the emergence of the Climate Disclosure Standards Board and the controversies around generating tradable carbon offsets from forestry projects in the UK, the immense technical, cognitive, social and political work required to make carbon measurable, commensurable and thereby amenable to various forms of management. The thesis contributes to both conceptual and practical understanding of carbon accounting as an emerging field of study. Bringing together a wide range of empirical examples of different types of carbon accounting practices, it proposes a unique definition of carbon accounting which expands the horizons of the field. It provides a conceptual basis for making sense of carbon accounting by considering it not as a unitary phenomenon but rather as a set of overlapping frames, each associated with different communities of practice. It shows that competence in carbon accounting is contested, particularly where these frames overlap, and that boundary organisations are emerging that offer the opportunity to negotiate such tensions and lead to more productive policy-making. Finally, it makes the case that engagement with the detail of the ‘nuts and bolts’ of carbon accounting is essential, as these apparently technical details can have major implications for the effectiveness of society’s response to climate change, and it is only by opening them up to rigorous scrutiny that we can make progress, both conceptually and practically.