The case involved a legal contention over the retroactive implementation of a 2010 amendment to Section 40(a)(ia) of the Income Tax Act, 1961, as the Commissioner of Income Tax, Kolkata, ... contested the rulings of the Income Tax Appellate Tribunal and the High Court of Calcutta favoring M/s Calcutta Export Company, with the central question being whether the amendment permitting TDS expense deductions for payments made before return deadlines should be effective retroactively from 2005 or only from the assessment year 2010-11 onward.