Using GHG accounting tools (in highly developed agricultural systems) is complex and costly. Great experience is needed for a meaningful interpretation of results. High diversity in methodologies, scope and emission allocation makes comparisons across different tools impossible. Transparency is key for a meaningful interpretation of results. Evaluating achievements is difficult and a fair (result based) benchmark and reward systems is barely possible. Different reporting units and benchmark approaches should be considerer together with possible system interactions. GHG accounting tools are particularly useful when embedded in an consultancy context with professional users.