I have opened a trading a/c with zerodha & a demat a/c with il&fs. My question is how do i give delivery instruction online in il& fs when I sell any share? Pls explain precisely

If you have opened the IL&FS demat account through Zerodha, then the shares that you have purchased will reflect in your holdings in backoffice as well as the trading platform. You can sell these shares directly from the trading platform by selecting the product code CNC.

But, if you have linked an IL&FS demat account (which you have opened through some other broker) to your Zerodha trading account, then you will only be able to buy shares through the zerodha trading platform but you will not be able to sell those shares as it will not be reflecting in the holdings. This is because the shares would have been credited to the demat account which is with the other broker and you will have to login to their backoffice to check your holdings.

Dear faisal, my question was that after selling, how do i give delivery instruction online or there is no need for giving delivery instruction?

When you opened an account, you would have signed a POA which will allow your broker to debit shares on sale. There’s no need to issue a DIS.