Through the CBIT-GSP project, countries within the 10 Transparency Networks can request support for preliminary peer-to-peer quality assurance checks of their BTRs prior to submission to the UNFCCC. In 2024, CBIT-GSP conducted over 40 of these QA checks, using an internal MPG-aligned Excel review tool. In this peer-to-peer process, the CBIT-GSP team and other UNEP-CCC experts offered prescriptive feedback on structure, content, and alignment of their BTRs, or specific chapters, against the Modalities, Procedures and Guidelines (MPGs), providing recommendations and opportunities for countries to enhance their reporting prior to submission. In conducting these reviews, a number of common gaps, inconsistencies, and reporting challenges were identified across the different chapters. Using the information gathered by the CBIT-GSP undertaking these reviews, a set of knowledge products which consolidates the lessons learned from the QA reviews, with a focus on identifying systemic gaps and assessing the capacity support required to enhance future BTR submissions has been developed. By highlighting recurring issues and showcasing best practices, it aims to contribute to improved reporting quality and greater transparency under the Paris Agreement. This knowledge products contains the information on Chapter I of the BTR: National inventory report of anthropogenic emissions by sources and removals by sinks of greenhouse gases