This short policy-oriented study seeks to contribute to the elaboration of the rulebook for carbon market instruments under Article 6 of the Paris Agreement. The tax on market mechanism activities (officially called “Share of Proceeds (SOP)”) is a key topic and priority for the African Group of Negotiators and other alliances. The objective of the study is to enhance the base of evidence for this discussion by providing an analytical background on previous experiences with the SOP under the CDM and current technical options as an input to the political negotiations. This study has been prepared in the context of the project Climate Finance Innovators – Linking carbon markets with climate finance in Africa.