Capital gains on property bookings

My client booked a immovable property, a Flat. But before its completion, due to financial difficulty, my client decided to surrender the booking. The booking was cancelled more than 3 years after the booking date, with the consent of the builder and the booking amount returned along with a premium for staying in it for more than 3 years. My query is should this premium on cancellation of booking be treated as Capital Gains and taxed accordingly?