The case involved a legal contention over the retroactive implementation of a amendment to Section a ia of the Income Tax Act 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 or only from the assessment year - onward