Income-tax Act, 1961
When, in the course of the assessment of the total income of any assessee, it is established that a loss has taken place which the assessee is entitled to have carried forward and set off under the provisions of sub-section (1) of section 72, sub-section (2) of section 73, [ [sub-section (1) or sub-section (3) of section 74] or sub-section (3) of section 74A], the [Assessing Officer] shall notify to the assessee by an order in writing the amount of the loss as computed by him for the purposes of sub-section (1) of section 72, sub-section (2) of section 73, [ [sub-section (1) or sub-section (3) of section 74] or sub-section (3) of section 74A].