This Guidance document (GCI) provides practical information on how the Core Indicators for Sustainability and SDG Impact Reporting can be measured in a consistent manner and in alignment with countries' needs on monitoring the attainment of the SDG Agenda. It is intended to serve as a tool to assist governments in assessing the private sector contribution to the SDGs, enabling them to report on SDG indicator 12.6.1. It also intends to assist entities in providing data on sustainability issues in a consistent and comparable manner. Beyond the objective of SDG impact measurement, the GCI also facilitates capacity building in the area of sustainability reporting in general.