Rectification under section 154 is limited to patent mistakes, not debatable issues requiring detailed inquiry.

Rectification under section 154 is limited to mistakes that are obvious, patent and apparent on the face of the record. Where identifying the error requires investigation, argument or a detailed process of reasoning, the matter falls outside rectification. On the facts discussed, there was a genuine controversy whether the business was a reconstituted firm or a succession of one firm by another, and the assessment order showed separate income computation and depreciation allowance for the two periods. In that setting, the omission to aggregate the two periods could not be treated as an apparent mistake, so section 154 did not permit rectification.

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Issues: Whether the omission to levy tax on the assessee firm in respect of the income for the period April 1, 1957, to June 10, 1957, was a mistake apparent from the record rectifiable under section 154 of the Income-tax Act, 1961.

Analysis: Rectification under section 154 is confined to mistakes that are obvious, patent and apparent on the face of the record. If determining the error requires investigation, argument or a long drawn process of reasoning, the case falls outside the rectification power. On the facts, there was a real controversy whether the business represented a reconstituted firm or a succession of one firm by another. The assessment order also showed separate computation of income and separate allowance of depreciation for the two periods, which supported the view that the assessing officer may not have intended to club both incomes. In that situation, the omission to aggregate the two periods could not be characterised as an apparent mistake.

Conclusion: The omission was not a mistake apparent from the record and was not rectifiable under section 154; the question was answered in the negative, in favour of the assessee.

Ratio Decidendi: A rectifiable mistake must be patent from the record itself and cannot depend on debatable issues or a detailed inquiry into competing legal or factual positions.

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