Allowing the petition the Court held that , merely because the assesse has shown capital gains as taxable in the return , the same cannot be taxed if it is not taxable . It is the duty of the Assessing Officer to refrain from assessing such income . Under article 265 of the Constitution The powers of the Assessing Officers under the Act are quasi-judicial in nature and they are duty-bound, therefore, to act fairly in the discharge of their functions. They are also invested with the authority to do justice to the assessees. In a case where it is apparent on the face of the record that the assessee has included in his return, an income which is exempted from payment of Income-tax, on account of ignorance or by mistake, the Assessing Officer is bound to take into account that fact in a proceeding under section 143 of the Income-tax Act, 1961 . In other words, if the capital gains on a transaction are exempted from payment of tax, the Assessing Officer has a duty to refrain from levying tax on the capital gains and the Assessing Officer cannot, in such cases, refuse to grant relief under section 143 of the Act to the assessee on the technical plea that the assessee has not filed a revised return. It is so since the paramount duty of the Assessing Officer is to complete the assessments in accordance with law ( AY. 2014-15)