Key messages and recommendations - The operational rules of Article 6.4 under the Paris Agreement would influence the supply of carbon credits on the market; however, the demand for credits cannot be controlled entirely by these rules. A realistic assessment of credit supply and demand should be used as the basis to determine the amount of Certified Emission Reductions (CERs) that are eligible for the use in Article 6.4, specifically since the NDCs are way below the required reduction to limit the increase in temperature well below 2 0C. The Clean Development Mechanism (CDM) under the Kyoto Protocol was successful in bringing new opportunities to reduce greenhouse gas emissions. However, the rules of Article 6.4 under the Paris Agreement should aim to address the challenges other opportunities faced from rules and procedures of, such as energy efficiency projects. It is important for climate negotiators and policymakers to strategically design the Article 6.4 mechanism to meet the needs of market participants, notably regarding how to ensure environmental integrity and incorporate sustainable development elements. Concrete solutions must be developed to incentivize the generation of sustainable development co-benefits from the projects contributing climate mitigation.