"Prevent unauthorized transactions in your demat/Trading account --> Update your mobile numbers/email IDs with your stock brokers/Depository Participant. Receive information of your transactions directly from Exchange/CDSL on your mobile/email at the end of the day. Issued in the interest of investors" 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. "No need to issue cheques by investors while subscribing to IPO. Just write the bank account number and sign in the application form to authorise your bank to make payment in case of allotment. No worries for refund as the money remains in investor's account."