Issue-wise bar on revision under tax law applies only to matters actually decided by the Tribunal, not the entire assessment.

Section 20(2-A) bars revision only on the specific issue that was the subject of, and actually decided in, the prior Tribunal appeal; it does not immunise the entire assessment from revisional scrutiny. The earlier appeal concerned only the one-time addition sustained by the Appellate Deputy Commissioner, while the correctness of the ten-times estimated addition was neither raised nor adjudicated. The Tribunal's powers under section 21(4) to confirm, reduce, enhance or annul an assessment are enabling only, and the absence of enhancement does not cause all assessment issues to merge in the appellate order. The statutory bar operates issue-wise, not assessment-year-wise.

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Issues: Whether the revisional authority was barred under section 20(2-A) from revising the assessment when the earlier appeal before the Tribunal had decided only one part of the turnover dispute, and whether the Tribunal's powers under section 21(4) made the whole assessment final so as to oust revision.

Analysis: Section 20(2-A) bars revision only in respect of an issue or question that was the subject-matter of an appeal before the Tribunal or was decided by it. The earlier appeal before the Tribunal concerned only the one-time addition sustained by the Appellate Deputy Commissioner; the correctness of the ten-times estimated addition was neither raised nor decided there. The Tribunal's power under section 21(4) to confirm, reduce, enhance or annul the assessment is only enabling and does not mean that, merely because no enhancement was made, every part of the assessment merged in the Tribunal's order or became immune from revision. The statutory bar operates issue-wise and not on the assessment year as a whole.

Conclusion: The revisional order was not barred by section 20(2-A), and the Tribunal was right in dismissing the challenge to it.

Ratio Decidendi: The bar against revision under section 20(2-A) applies only to the specific issue decided by the Tribunal, and not to other issues in the same assessment that were neither raised nor adjudicated in the prior appeal.

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