In this report, a habitat-oriented approach is used to assess marine carbon stores in the English North Sea and its Marine Protected Areas (MPAs). “Blue carbon” habitats are broadly considered here as essentially all those habitats with significant contributions to the fixation and storage of carbon. Such habitats present in the area are identified and reviewed for their potential to fix and store (sequester) carbon, focussing on the ecology of the key carbon-fixing and habitat-forming species, the dynamics of physical habitats, and quantitative estimates of stocks and rates of carbon fluxes. Exports and imports from these habitats, threats to stocks and fluxes as well as the potential of restoring lost habitats to improve carbon storage and sequestration. Habitat reviews (Section 2) have identified sources of information on known and predicted habitat extent and combined these into maps and associated GIS data files. This collected information is used to synthesise an ecosystem-scale carbon inventory of the key rates and ultimate sequestration capacity of each habitat. The resulting synthesis and assessment of carbon sequestration capacity will guide conservation and restoration efforts in the region. Assessing carbon sequestration and storage in the region follows the sequence of combining estimates of area with area-specific rates of production, loss, import and export of carbon, and thence area-specific rates of sequestration, to give area-integrated estimates of the total amount of carbon locked away by biological activity in the coastal zone. The approach follows that of successful and widely used audits of carbon storage and sequestration processes, primarily the review of Scotland’s blue carbon stocks (Burrows et al., 2014). This was the first national assessment of its kind, and remains the primary source for information on carbon stocks in the area as habitat-specific estimates continue to be revised (Turrell, 2020). Partitioning blue carbon stocks and processes among MPAs in Scotland informed the role of MPAs in protecting the capacity of coastal seas to sequester carbon (Burrows et al., 2017). Integrating the contribution of UK coastal areas with European shelf waters recently produced a continental shelf-wide assessment of carbon dynamics (Legge et al., 2020) and the first complete mapping of sedimentary carbon across the UK EEZ (Smeaton et al., 2021).