To dematerialise its shares, a company must pass a board resolution to convert its physical securities to demat. For this purpose, it must appoint a registrar and transfer agent (RTA) who will act as an intermediary to record and maintain transactions of the investors in the demat form.
In case of secondary transactions of shares held in demat form, the RTA must get a confirmation from the company before approving the transfer. After this, the RTA can register the transfer in demat mode.