Self-assessment return due date governs filing and payment; late filing beyond the prescribed deadline is not permitted.

Under the Tamil Nadu General Sales Tax Act, 1959, the monthly return in self-assessment must be filed, and tax paid, by the 20th of the succeeding month. Section 13(2) read with rule 18(2) fixes that date as the prescribed limit, and the phrase "whichever is later" permits payment up to the last due date but does not authorise filing the return after that date. An interpretation allowing late filing would undermine the statutory scheme for timely return filing, tax recovery, and penalty for default. The prescribed last date therefore governs both filing and payment.

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Issues: Whether, in the case of self-assessment under the Tamil Nadu General Sales Tax Act, 1959, a dealer can file the return after the 20th of the succeeding month and contend that the tax becomes due only on the date of filing of the return, so as to avoid penalty under the Act.

Analysis: Section 13(2) of the Act, read with rule 18(2) of the Tamil Nadu General Sales Tax Rules, 1959, fixes the due date for filing the monthly return and payment of tax as the 20th of the succeeding month. The expression that the tax becomes due on the date of receipt of the return or on the last due date as prescribed, whichever is later, was held to permit payment at any time up to that prescribed last date, but not to authorise filing of the return beyond that date. An interpretation allowing filing after the prescribed date would defeat the scheme of section 13(2), rule 18(2), and section 12(5) of the Act, which together provide for timely submission and recovery of tax and levy of penalty for default.

Conclusion: A dealer in self-assessment cannot file the return after the 20th of the succeeding month and avoid the statutory consequence of delay; the prescribed last date for both filing the return and payment of tax is the 20th of the succeeding month.

Ratio Decidendi: In self-assessment under the Act, the statutory due date fixed by the Rules governs both filing of the return and payment of tax, and the phrase "whichever is later" does not permit filing beyond the prescribed last date.

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