Capital Gains

Thanks Sir ! In a case the JDA was entered into with the developer  in August 2019,that is financial year2019-2020 relevant  to the assessment  year 2020-2021 The JDA was not registered. The possession  of the land handed over to the developer and after obtaining necessary  sanction from the corporation authorities the work is under progress. In this case when does the capital gain arises and which assessment  year capital  gain tax has to be given