This Recommendation provides methodology for assessing how the use of ICT solutions impacts GHG emissions of other sectors. More specifically, the methodology provides guidance on the assessment of the use of ICT solutions covering the net second order effect (i.e. the resulting second order effect after accounting for the emissions due to the first order effects of the ICT solution), and the higher order effects such as rebound. By providing a structured methodological approach, it aims to improve consistency, transparency and comprehensiveness of assessments of how the use of ICT solutions impact GHG emissions over time. Guidance is provided to assess the net second order effect and higher order effects of the following cases: - ICT solution(s) implemented in a specific context by the user of the ICT solution - ICT solution(s) implemented at different scales, including at an organizational level (whether private or public organizations), at a city level, at a country level or at worldwide level. - ICT solution(s) seen from the perspective of an ICT organization contributing to the ICT solution. This includes o Assessment of the aggregated effect of all ICT solutions provided by an ICT organization across all its customers o Assessment of the aggregated effect of one or several ICT solution(s) provided by an ICT organization across some of its customers o Assessment of the effect of one or several specific ICT solution(s) implemented in an actual context for a specific customer.