BO ID in Zerodha stands for Beneficiary Owner Identification Number, which is a 16-digit number that identifies a demat account. It is a unique identification number provided to every client that is registered with a stockbroker in the stockbroking industry. BO ID is the demat account number or the unique identification number provided to you at the time you open an account with the broker. You can find your BO ID in the trading platform - Zerodha Kite. When you log into the platform, click on the tab that reads your Login ID. When the screen loads, click on My Profile. BO ID is required when applying for IPOs and generating the CDSL TPIN for holdings authorization.