Tatkal tickets booked through IRCTC's website and mobile app, through Passenger Reservation System counters, and authorised agents will require mandatory Aadhaar-based OTP authentication, starting July 15. Tatkal bookings open at 10 am for AC and 11 am for non-AC classes one day before the train's departure. The IRCTC agents won't be allowed to book tickets for the first 30 minutes.