Industry guidelines developed jointly by CLEPA and OICA to provide a harmonised methodology for determining the carbon footprint of passenger cars through their full life cycle, from material extraction through production, use, and end-of-life. The guidelines establish four levels of assessment based on data granularity and intended application (ranging from public policy analysis to detailed supply-chain reporting), with fixed methodological approaches for Levels 3 and 4. They specify treatment of GHG emissions including biogenic carbon, land use change, and fossil emissions; define data quality requirements including primary data collection and allocation procedures; and establish system boundaries across material production, parts and vehicle assembly, use, and end-of-life stages, employing the Circular Footprint Formula for material recycling assessment.