Résumé : The contentious 15th Conference of the Parties (COP) to the United Nations FrameworkConvention on Climate Change (UNFCCC) held in Copenhagen in 2009 eventually led to anunprecedented commitment by developed countries to provide funds to help developing countriesmitigate their greenhouse gas emissions and adapt to the adverse effects of climate change. Yet, theconstruction of systems to ensure real transparency in funding delivery has largely been neglected oravoided so far, and opportunities for inclusivity and trust-building have been missed.As the analysis – summarized in this working paper – made by AdaptationWatch (2015)demonstrates, many developed countries have so far failed to be transparent and complete in theirreporting to the Convention with regard among others to their financial accounting methodologies andtheir definition of “new and additional” climate finance. While each Annex II Party can be heldaccountable for failing to provide transparency in its own reporting to the Convention, we argue thatthe current lack of transparency also is a collective failure. Indeterminate language in UNFCCCdecisions has given developed countries almost complete discretion with regard to the implementationof their climate finance pledges. As this working paper explores, contributing countries have been ableto interpret key issues that are contested in the negotiations. The UNFCCC reporting guidelines leaveconsiderable discretion for a range of accounting approaches, which greatly impedes comparisonsbetween developed countries’ performance.In the current climate finance landscape, each developed country has an interest in maximizing itsclaimed contribution while putting up the least cash possible (including through non-transparent and“creative” accounting), and in putting the burden on other developed countries to implement jointfinancial commitments (or to be creative in their accounting, as well). The two victims of thesepractices are first the trust between developed and developing countries in international climatenegotiations, and second the vulnerable populations and nations in dire need of help. This workingpaper sets out a number of recommendations that could bring a quantum-leap in the transparency andeffectiveness of international climate finance. These would go a long way to establishing a robustaccounting and reporting system, improving trust to boost the climate negotiations.