Advance tax interest turns on the original assessment date, not a later appellate giving-effect order.

For interest on advance tax under section 18A(5), the expression "regular assessment" refers to the first or original assessment under section 23, because that is the point at which the assessee's liability is crystallised and compensatory interest ceases to be relevant. A later assessment made only to give effect to an appellate order does not shift the relevant date for interest computation. The legislative scheme, including the contrast with section 18A(6) and its express provision for recomputation on appeal, supports that interest calculations ordinarily relate back to the original assessment framework. Accordingly, no interest was payable on the excess advance tax beyond that original assessment date.

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Issues: Whether, for the purpose of interest on advance tax under section 18A(5), the relevant date is the date of the first or original assessment under section 23 or the date of an assessment order passed to give effect to an appellate order.

Analysis: Section 18A(5) was construed in light of its legislative history and its scheme of compensating the assessee for the period during which advance tax is paid before liability is crystallised by the original assessment. The reference to the assessment made under section 23, described as the regular assessment, was held to mean the first or original assessment order for the year. Once that assessment is made, the assessee's liability to pay arises and the basis for compensatory interest disappears. The converse provision in section 18A(6) and its express proviso for recomputation on appeal reinforced that, absent such special language, interest computations ordinarily relate back to the original assessment order.

Conclusion: The relevant date is the date of the first or original assessment order, not the date of the order passed to give effect to the appellate decision. No interest was payable under section 18A(5) on the facts, and the contention of the assessee failed.

Final Conclusion: The writ petition was rejected because the assessee had no entitlement to interest on the excess advance tax beyond the original assessment framework, and the impugned revenue action was upheld.

Ratio Decidendi: For interest payable on advance tax under section 18A(5), the expression 'regular assessment' means the original assessment under section 23, and not a later consequential assessment made to implement appellate relief.

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