What should I do if I notice an unauthorised trade?

You act immediately rather than waiting to see if it resolves itself: you first change your trading account password and log out of all active sessions to cut off any ongoing unauthorised access. Then you contact the broker’s support team right away, specifically flagging it as an unauthorised transaction, since brokers have defined timelines (often set by SEBI guidelines) within which such complaints need to be raised and investigated. You document everything, the specific trade details (time, stock, quantity, price), screenshots if available, and any suspicious login alerts you might have received around that time, since this documentation matters if the case needs to go further. If the broker’s response is unsatisfactory or delayed, you escalate through SEBI SCORES (the SEBI Complaints Redress System) or the exchange’s investor grievance mechanism, since an unauthorised trade is a serious issue that shouldn’t be left only to informal resolution with the broker.