ISIN (International Securities Identification Number) is a 12-character alphanumeric code that uniquely identifies a specific security globally.

For Indian securities, ISIN begins with "IN" followed by 10 characters.

Structure: IN + 9 characters + check digit Example: INE542A01019

In SGB context, each SGB series has a unique ISIN which: - Identifies it uniquely across all exchanges globally - Is required for demat account operations - Used in corporate actions and settlements - Helps distinguish between different SGB series

ISIN is assigned by NSDL (National Securities Depository Limited) for Indian securities.