The indirect impacts of Information and Communication Technology (ICT) on the environment (whether positive or negative) have been extensively discussed in academic and industrial literature, particularly within the ICT4S community. However, a lack of consensus exists in academia on how to assess them, especially in the context of decision-making processes. This paper examines whether ‘net impacts accounting’ methods are suitable for decision-making and suggests alternative approaches. We begin by clarifying different scenarios within the context of environmental decision- making. Then, we assess their relevance across those different decision scenarios. We emphasize their inadequate response to uncertainties, their focus on solutions rather than problems, and their inability to inspire a range of decisions compatible with an environmental transition. Drawing insights from systems thinking, we finally suggest methods and tools that could be combined to better address the complexity surrounding environmental decision-making. Throughout the paper, we develop the case study of Vinted – a second-hand clothing resale platform – to illustrate our arguments. The contribution advocates for a more systemic approach that embraces complexity by employing mixed methods, encompassing both qualitative and quantitative perspectives.