Best judgment assessment must rest on a rational, bona fide estimate and cannot be displaced without material showing arbitrariness.

A best judgment assessment based on current consumption can be sustained where the estimating officer acts honestly and on a rational, recognised method. An appellate or revisional authority should be slow to interfere with such an estimate and should not replace it with a different percentage-based approach without intelligible reasons or supporting material. Interference is warranted only if the estimate is shown to be dishonest, arbitrary, capricious, irrational, or unsupported by material. On these principles, the Tribunal's reversal of the assessing authority's estimate was unsustainable.

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Issues: Whether the Tribunal was justified in reversing the assessing authority's best judgment estimate based on current consumption, and whether such interference was warranted in the absence of material showing that the estimate was dishonest, arbitrary or irrational.

Analysis: A best judgment assessment may involve some guesswork, but the estimate must be made honestly and on a rational basis. A revisional court should be slow to interfere with pure findings of fact, and the same caution applies to the appellate authority, which should not discard a well-accepted estimate supported by material merely because it prefers another method. Where the assessing authority adopted a method recognised in earlier decisions and the Tribunal substituted a different percentage-based method without intelligible reasons or supporting evidence, the interference was unsustainable in principle.

Conclusion: The Tribunal was not justified in reversing the assessment on the basis adopted by the assessing authority, and its interference was erroneous in law.

Ratio Decidendi: An appellate authority should not disturb a bona fide best judgment estimate based on a recognised and rational method unless the estimate is shown to be unreasonable, capricious, or unsupported by material.

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