This article reviews critical social science analyses of carbon accounting and monitoring, reporting and verification (MRV) systems associated with reducing emissions from deforestation, forest degradation and conservation, sustainable use and enhancement of forest carbon stocks (REDD+). REDD+ MRV systems are often portrayed as technical. In questioning such a framing, we draw on perspectives from science and technology and governmentality studies to assess how MRV systems may exercise disciplinary power (through standardization, simplification and erasing the local) but also mobilize counter-expertise, produce resistance and thus have necessarily contingent effects. In doing so, we advance the concept of 'carbon accountability' to denote both how forest carbon is accounted for in REDD+ and the need to hold to account those who are doing so.