"Prevent unauthorised transactions in your account/demat account --> Update your mobile numbers/email IDs with your stock brokers/Depository Participant. Receive alerts on your Registered Mobile for all debit and other important transactions in your Demat Account directly from CDSL on the same Day. .......... Issued in the interest of Investors"
Share Broking, Online trading

"KYC is one time exercise while dealing in securities markets - once KYC is done through a SEBI registered intermediary (broker, DP, Mutual Fund etc.), you need not undergo the same process again when you approach another intermediary."