Hey, if you go for the railway station for the cancellation, the refund depends on the time you do it. If you return it more than 15 days in advance, it would be for free. If it is more than 48 hours in advance, the cancellation fee would be 5%, if between 24 hours to 48 hours, it would be 10% and if less than 24 hours, it would be 20%. You need to do it before the departure time, once the time passes, it cannot be returned. If you book from a online agent, it would be different can based on their policy. You need to ask them in details.