Yes, you can transfer your existing shares in another broker's demat to your Zerodha demat account. There are two types of transfer of holdings between demat accounts- intra-depository transfer and inter-depository transfer. The type of transfer depending on your current central depository of the demat account, NSDL and CDSL. If the central depository of both the demat accounts is the same then it will be an intra-depository transfer. For example, if both the demat accounts you're transferring shares are held with NSDL then its intra-depository transfer. Transfer of holding between a NSDL demat account and a CDSL demat account and vice versa is called inter-depository transfer.
To transfer shares from one demat to another, you need to use the Debit Instruction Slip (DIS) booklet provided by your Stock Broker. Here, you have to enter the names of shares along with their unique ISIN numbers. Then you have to provide the Target Client id (a 16-character code consisting of the DP id and the client id). Next, you need to select the transfer mode selection- intra-depository or inter-depository.
Transferring of shares takes time. Also, every time you want to sell shares held in your non-zerodha demat account using zerodha trading platforms, you have to first transfer the shares to zerodha demat account. That's why it is recommended to open a demat account along with a trading account with Zerodha.
