Section 170A limits completed assessments to modification for amalgamation; fresh scrutiny notices were invalid.

Where section 170A(2)(a) applies because the assessment was already completed when the modified return was filed, the Assessing Officer's power is limited to modifying the existing assessment to reflect the business reorganisation order and the modified return. The provision does not authorise a fresh or de novo scrutiny of the entire return through notices under sections 143(2) and 142(1), which are reserved for pending proceedings under clause (b). The notices issued for reopening the completed assessment were therefore unsustainable, and the consequential assessment order was set aside.

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Issues: Whether, in a case governed by section 170A(2)(a), the Assessing Officer could issue notices under sections 143(2) and 142(1) to reopen the entire assessment, or was confined to modifying the completed assessment to give effect to the amalgamation order and the modified return.

Analysis: Section 170A creates a distinct framework for business reorganisation. Where the assessment or reassessment stood completed on the date of the modified return, clause (a) requires the Assessing Officer to pass an order modifying the total income determined in the completed assessment in accordance with the reorganisation order and the modified return. The provision draws a clear distinction from clause (b), which applies only where assessment proceedings are pending and permits assessment or reassessment. In the completed-assessment situation, the statutory scheme does not permit a fresh or de novo scrutiny of the entire return through notices under sections 143(2) and 142(1); the inquiry is limited to giving effect to the reorganisation and the modified return.

Conclusion: The notices under sections 143(2) and 142(1) were unsustainable and were quashed, and the consequential assessment order was also set aside.

Ratio Decidendi: When section 170A(2)(a) applies because the assessment is already completed on the date of the modified return, the Assessing Officer's power is confined to modifying the existing assessment to give effect to the business reorganisation order and cannot be used to reopen the assessment by issuing notices for a fresh scrutiny.

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