The Tatkal Scheme is a ticketing program established by Indian Railways.The scheme is used for booking journeys at very short notice. Railway minister Nitish Kumar introduced it in all forms of reserved classes on almost all trains in India.
Tatkal scheme Wikipedia
Tatkal tickets can be booked over the counter in a railway station and on the internet at IRCTC.Ticket booking opens at 10:00 AM on the day before the journey. The day of the journey is defined as the day of chart preparation.
Booking starts at 10:00 AM for air conditioned coaches. For sleeper coaches it starts from 11:00 am.
No entire trains are defined as Tatkal trains. Unsold Tatkal tickets are released to passengers on a waiting list. Confirmed Tatkal tickets can be cancelled, but no refunds are given. Tatkal tickets on the waiting list may be cancelled and refunded.
On those trains and in those cases where the average utilization of Tatkal accommodation during the peak period of April to September is 80% and above, the Tatkal charges that are applicable during the peak period will be charged throughout the year, i.e., for both the peak and the non-peak periods.
Premium Tatkal was introduced on October 1, 2014 covering half of the tickets on certain trains. These tickets can be purchased online only. The program began with a pilot of about 80 trains. Premium Tatkal and regular Tatkal tickets operate in the same manner.
Misuse of this scheme led the Ministry of Railways to change the timing of Tatkal bookings in June 2015. Ticketing agents, including IRCTC agents, are prohibited from booking non-Tatkal tickets for 30 minutes from the opening of bookings.