The following precautions are to be taken :-

Ensure and insist with your DP to issue DIS book; do not accept loose slips. Ensure that DIS numbers are pre-printed and DP takes acknowledgment from you for the DIS booklet issued to you.

Ensure that your account number [client id] is pre-stamped. If your account is a joint account, all the joint holders have to sign the instruction slips. Instruction cannot be executed if all joint holders have not signed.

Avoid using loose slips Do not leave signed blank DIS with anyone viz. broker/sub broker. Keep the DIS book under lock and key when not in use. If only one entry is made in the DIS , strike out remaining space to prevent misuse by any one.
Please fill in target account -Id and all details in the DIS, yourself.