The UKCP18 21st Century regional time-mean sea level projections are based on CMIP5 climate model simulations of global ocean thermal expansion and global average surface temperature (GST) change. Global contributions from ice sheet surface mass balance and glaciers are related to GST following methods described in IPCC AR5 WG1 Chapter 13 (Church et al, 2013). Global sea level contributions for dynamic ice discharge for Greenland and Antarctica are based on IPCC AR5 and Levermann et al (2014), respectively. Estimates of land water storage changes follow those reported in IPCC AR5. These global components are regionalised for the UK through use of: (i) sea level fingerprints for mass components provided by Aimee Slangen and Giorgio Spada; (ii) regression relationships around the UK and across CMIP5 models for the oceanographic component; (iii) an ensemble of estimates of the relative sea level change from glacial isostatic adjustment from the NERC BRITICE_CHRONO project. Following the approach of Church et al (2013), a 100,000 sample Monte Carlo is used to provide uncertainties for regional sea level change based on the 5th and 95th percentiles of the Monte Carlo sample. Please refer to UKCP18 documentation for detailed methods.