RAC ticket kab taq cancel kar sakte he
But chart is prepared, we can, I think ,cancel before 30 minutes of departure
Refund on unused RAC/WL tickets: Upto half an hour before the scheduled departure of the train subject to deduction of clerkage charge. No refund after the above prescribed time limit.
W.e.f 12th November 2015, if a ticket having all passengers as waiting list or RAC or some passengers having waiting list while some as RAC is surrendered for cancellation at least 30 minutes before the train departure, entire amount is refunded after deducting clerkage charge which is Rs.60 per passenger. This remains same across all travel classes. No refund is given if less than 30 minutes is remaining in train departure. However, if an e-ticket has all passengers as waiting list, it gets automatically canceled and amount is refunded to passengers account.
You can get more details on cancellation charges by visiting the following link :