This fifteenth annual report of the administrator of the international transaction log provides information to the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol (CMP) on the activities of the administrator of the international transaction log in the period from 1 October 2018 to 30 September 2019. It contains information on transactions of Kyoto Protocol units, as requested at CMP 6, and information on the outcomes of the 21^st Registry System Administrators Forum, which took place in Copenhagen on 2 October 2019.