We can refer to section 56(2)(ix) of the Income Tax Act for this question. Wherein it is provided that:

(ix) any sum of money received as an advance or otherwise in the course of negotiations for transfer of a capital asset, if –

(a) such sum is forfeited; and

(b) the negotiations do not result in transfer of such capital asset

Therefore the tax treatment shall be that the amount forfeited will taxable under the head income from other sources.