The BGS Permeability Index dataset shows estimated rates of water movement from the ground surface to the water table. The v8 dataset incorporates the latest geology mapping (BGS Geology 50k). This includes updates to the lithology-coding schema, the LEX_RCS. A 2-part code used to identify the named rock unit from the BGS lexicon of named rock units (LEX) followed by a Rock Classification Scheme (RCS) code which describes the rocks lithological characteristics e.g. texture and composition. Updates to these codes and latest dissolution hazard data sourced from BGS GeoSure: Soluble Rocks have been reviewed and classified as part of the version 8 release. The dataset covers Great Britain and is presented at a scale of 1:50 000, based on the geological data at the same scale. However, in areas where the geology is not mapped to this scale, the next best available scale is used. The BGS Permeability Index can be used to compare the relative permeability of deposits at the regional scale, indicating where highly permeable rocks could allow rapid infiltration to occur, or where less permeable rocks are present and water could pond on the ground surface. The dataset can be used as a component in a wide range of geo-environmental assessments such as natural flood management, Sustainable Drainage Systems, engineering desk studies, slope stability, and aquifer vulnerability. It is for use at the regional scale and is not recommended for use at the site-specific scale.