The dataset details vegetation composition of UK saltmarshes measured from quadrats across UK saltmarshes. Between 2018 and 2021, vegetation surveys were carried out at 460 sites across 33 saltmarshes as part of the Carbon Storage in Intertidal Environments (C-SIDE) project to develop an understanding the linkages between saltmarsh soil organic carbon and vegetation. Sites were chosen to represent contrasting habitats types in the UK, in particular sediment types, vegetation and sea level history. The dataset comprises of percentage species cover, plant height, plant richness and plant diversity data from 33 UK saltmarshes. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1.