Section 12(1) in The Railway Passengers (Cancellation of Ticket and Refund of Fare) Rules, 2015
(1)Change of reservation shall be allowed on a reserved ticket of lower class for higher class on the same train and day without levying any cancellation charges but on payment of fresh reservation fee and difference of fare, if any, for higher class subject to the condition that -(i)accommodation is available; and(ii)the request for change is made -(a)either during the working hours of reservation office and upto six hours before the scheduled departure of the train subject to restriction on timings of this facility imposed by railway administration from time to time; or(b)during the course of journey in the train.
