State Of A.P vs National Thermal Power Corpn. Ltd. & Ors

The Supreme Court held that the levy of duty on sales of electrical energy by the National Thermal Power Corporation Ltd. (NTPCL) under the Andhra Pradesh Electricity Duty Act, 1939 is unconstitutional as it pertains to inter-State sales, thus outside the legislative competence of the State Legislature. The Court affirmed the High Court's decision that the tax levied was without authority of law and ordered a refund of the collected amounts. The judgment clarified the interpretation of Article 132 concerning substantial questions of law arising from the case.