Conditional instalment relief does not override statutory penal interest on defaulted arrears when express terms preserve liability.

Section 24(3) of the Tamil Nadu General Sales Tax Act, 1959, was treated as constitutionally valid because the challenge had already been rejected in earlier proceedings and could not be reopened. The instalment concession for arrears did not displace the statutory liability where the permission was expressly conditional, including payment of penal interest at 24 per cent on outstanding arrears until clearance. As the conditions were not fully complied with, section 24(3) continued to apply to the defaulted instalments, and the demand for penal interest was upheld.

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Issues: (i) whether the constitutional validity of section 24(3) of the Tamil Nadu General Sales Tax Act, 1959, could be successfully challenged; (ii) whether section 24(3) could be enforced for defaulted instalments despite permission granted to pay arrears by instalments under the Government order.

Issue (i): Whether the constitutional validity of section 24(3) of the Tamil Nadu General Sales Tax Act, 1959, could be successfully challenged.

Analysis: The provision had already been upheld as constitutionally valid in earlier proceedings. That binding position governed the challenge, and the Court treated the provision as valid notwithstanding its stringent operation.

Conclusion: The constitutional challenge to section 24(3) failed and was rejected.

Issue (ii): Whether section 24(3) could be enforced for defaulted instalments despite permission granted to pay arrears by instalments under the Government order.

Analysis: The instalment concession was granted subject to express conditions, including liability to pay penal interest at 24 per cent on outstanding arrears until clearance, with no waiver of such interest. Because the concession was conditional and the conditions were not fully complied with, the statutory liability under section 24(3) continued to operate in respect of the defaulted amounts.

Conclusion: Section 24(3) remained enforceable against the defaulted instalments and the demand for penal interest was upheld.

Final Conclusion: The writ petition was found to be without merit and was dismissed.

Ratio Decidendi: A conditional instalment concession that expressly preserves liability to penal interest does not displace the operation of the statutory provision imposing such interest on defaulted arrears, and a settled constitutional challenge to that provision cannot be reopened in collateral proceedings.

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