Valid jurisdiction for assessment requires specific written authorisation; absent that, the assessment cannot stand.

An assessment completed by an Additional Commissioner was invalid because he was not shown to have been authorised by a specific written order and was not otherwise treated as an Assessing Officer. The exhaustive definition of "Assessing Officer" did not itself include the Additional Commissioner, and jurisdiction could arise only through a written authorisation under the statute. A general administrative clarification could not replace the statutory requirement of a formal order in writing. Since statutory powers must be exercised in the prescribed manner, the assessment lacked valid jurisdiction and was quashed.

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Issues: Whether the assessment framed by the Additional Commissioner of Income-tax was valid when he was not shown to have been authorised by a written order under section 120(4)(b) and was not treated as an Assessing Officer within section 2(7A).

Analysis: The definition of "Assessing Officer" in section 2(7A) is exhaustive and does not, by itself, include the Additional Commissioner of Income-tax. A Joint Commissioner can exercise Assessing Officer functions only when empowered by a written order under section 120(4)(b) issued by the competent authority. The record did not show any such valid written authorisation transferring or conferring jurisdiction on the officer who completed the assessment. A general clarification or administrative instruction could not substitute the statutory requirement of a specific order in writing. Since a power conferred by statute must be exercised in the manner prescribed by the statute, the assessment made without valid jurisdiction could not be sustained.

Conclusion: The assessment was held to be without valid jurisdiction and was quashed, in favour of the assessee.

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