Kolkata Income Tax Applelate Tribunal in the case of Subhas Chandra Parmanandka (ITA No.1614/Kol/2010) held that income from transfer of right to purchase a flat is taxable as Capital gains. Compensation received over and above the booking amount is equivalent to consideration received on transfer of right to acquire property and is taxable under capital gains.
At the same time if the cancellation deed indicate the receipt as interest paid over the deposit amount, then the same will be added to your income under income from other sources, and will be taxed as per slab rate.
Refer: interest-on-refunds-from-builders-adds-to-tax-burden