Best judgment assessment rectification fails without cogent material, and merged assessment orders cannot be challenged by rectification.

Rectification of a best judgment assessment was unavailable where no cogent material was produced before the assessing, revisional, or revenue authorities to show an error apparent on the record in the inclusion of the disputed turnover. The absence of supporting material was treated as fatal to the claim. The Court further held that once an appellate order modified the original assessment, the original order merged into the appellate order and ceased to subsist for rectification. Any challenge had to be directed against the operative appellate order, so no mandamus could issue to compel consideration of rectification against the superseded order.

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Issues: Whether rectification could be invoked against a best judgment assessment when no cogent material had been placed before the authorities to show an error apparent on the record; and whether, after the assessment order had been modified in appeal, rectification could still be sought against the original order.

Analysis: Rectification under section 55 was held to be unavailable because the assessment had been made on best judgment and the petitioner failed to place acceptable material before the assessing authority, the revisional authority, or the Board of Revenue to establish that the disputed turnover was wrongly included. The Court treated the absence of such material as fatal to any claim of an apparent mistake. It further held that once an appellate order had modified the original assessment, the original order had merged in the appellate order and ceased to subsist for the purpose of rectification; any challenge had to be directed against the operative appellate order and not the superseded original order.

Conclusion: Rectification was not maintainable on the facts, and no mandamus could issue to compel the assessing authority to entertain the application.

Final Conclusion: The petition failed because the alleged mistake was never substantiated by material and the original assessment order was no longer the subsisting order after appeal.

Ratio Decidendi: Rectification of a best judgment assessment is not available in the absence of cogent material showing an error apparent on the record, and once an assessment order is superseded or merged in appeal, rectification must be sought against the operative appellate order alone.

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