Held, that in year under consideration, since no enforceable liability had accrued or arisen, it could not be said that the assessee had any vested right to receive the retention money. The assessee had no right to claim any part of the retention money till the verification of the satisfactory execution of the contract was over. Therefore, the retention money retained by the Electricity Board could not be treated as income of the assessee even though the assessee due to mistake of fact had offered it as income of this year in its return of income. When the assessee received or when this amount accrued to the assessee, it should be taxed in that AY and not in this AY. (AY. 2015-16, 2017-18 to 2019-20)