The assessee, a charitable trust, inadvertently claimed double deduction by claiming both depreciation and capital expenditure. Before completion of the assessment, it filed a revised Form No. 9A to increase the amount to be accumulated and carried forward. The Tribunal held that the tax authorities failed to ascertain the correct taxable income merely because the revised Form No. 9A was filed after the prescribed due date. Since the revised Form had been filed before completion of the assessment and could materially affect the computation of taxable income, the matter was restored to the Assessing Officer for fresh adjudication. (AY. 2020-21).