• The Circular – issued by the ministry’s Tax Research Unit (TRU), – explains that booking of tickets is a ‘contract’, under which the service provider (IRCTC/Indian Railways) promises to provide services to the customer.
• “When the contract is breached by the passenger, the service provider is compensated with a small amount, collected as a cancellation charge. Since the cancellation charge is a payment, and not breach of contract, it will attract GST,” the notification said.
• For canceling bookings of a particular class, the GST rate will be the same as that applicable while booking seats/berths for that class, it added. For example, the rate is 5% for first-class or AC coaches, while cancellation fee for this category is ₹240 (per passenger). Therefore, the total cancellation cost will be ₹252 ( ₹12 tax+ ₹240) for first-class/AC compartments. However, there is no GST on other categories, including second sleeper class
• Conditions for booking cancellation:
• However, the aforementioned ₹240 cancellation charge is applicable when the ticket is canceled 48 hours or more before the scheduled departure of the train. 

Source- https://www.hindustantimes.com/business/cancelling-confirmed-train-ticket-will-now-invite-gst-finance-ministry-101661743087792.html