Soon, the railways will allow the passengers get back the whole amount in the event of their cancelling the Tatkal ticket. The IRCTC is preparing the necessary guidelines for the same.
However, this facility would be available only if the designated train comes three hours late to the station. Also, if the train is either diverted or the destination is altered or if the railway fails to provide him berth, the passenger can cancel the ticket and can get back the full amount.
Similarly, if a passenger is given a berth in the lower class than the class for which he booked his ticket, he can cancel his ticket and get back the amount in full.