This paper addresses the need for a comprehensive global dataset on national greenhouse gas (GHG) emission inventories to support policy analysis and track progress towards climate change mitigation goals. While numerous datasets exist, gaps in official data, particularly from developing countries, hinder their utility. The paper develops a methodology to compile a complete dataset, prioritising official data reported to the United Nations Framework Convention on Climate Change (UNFCCC) and the OECD. To fill gaps, estimates based on unofficial datasets, such as PRIMAP, will be used, as they demonstrate the greatest alignment with official data in terms of emission levels, trends and categories. As official data become available under the Enhanced Transparency Framework of the Paris Agreement, estimated values would be replaced and additional data collection would not be necessary. The dataset disaggregates emissions by IPCC categories, gases, countries, and years, distinguishing between official data points and estimates. This harmonised dataset enhances transparency, improves data collection efficiencies, and enables more robust evidence-based policy analysis. Moving forward, the paper recommends refining the dataset with sector-specific data and fostering collaboration with international organisations to improve the reliability and consistency of global GHG emissions data and indicators.