Non-binding industry guidance developed jointly by CLEPA and OICA providing internationally harmonised methodology to determine carbon footprint of passenger cars across all life cycle stages. Guidelines define four levels based on data granularity and intended use cases, from generic strategic planning to detailed supply chain reporting. Specifies methodological requirements for material production, parts production and vehicle assembly, use stage, and end-of-life stages; includes requirements for data collection, energy modelling, waste treatment and recycling, and reporting. Applies 100-year global warming potential characterisation factors from IPCC, with dual reporting of carbon footprint including and excluding biogenic CO₂ uptake. Establishes primary data share indicators and chain of custody requirements for supply chain transparency.