The Tatkal seat availability can be checked on the below mentioned link http://www.indianrail.gov.in/seat_Avail.html
This URL is used for checking availability of seats for normal reservation also. The Tatkal seat availability of IRCTC can be checked by entering the specified information on the portal like Train Number, Journey date, source station code, destination station code, class of travel, quota etc. Otherwise Tatkal seat availability can be searched without train number, station code, or if you know the station code. The Tatkal seat availability of IRCTC also helps to know the vacant berth status on running trains for the convenience of the travellers.
In case if the ticket is not confirmed but has been on IRCTC Tatkal Waiting List then the confirmations under Tatkal Waiting List would arise only when there are cancellations among the Confirmed Tatkal Quota Bookings and those in Tatkal Waiting List would also be considered against the vacancies in the earmarked quotas except Ladies Quota. IRCTC Tatkal Waiting List can be checked like the ordinary ticket with the PNR number provided. If such a ticket is not required then it can be cancelled before 24 hours of the journey and refund would be available as per the Indian Railways rule.