Provisional assessment must follow statutory bases only; best judgment cannot replace the dealer's estimate or prior turnover.

Section 5(8) of the Mysore Sales Tax Act, 1957 permits provisional assessment only on the dealer's estimate or on the previous year's turnover. The assessing authority cannot discard those statutory bases and adopt a best judgment estimate under rule 16(b), because delegated rules cannot enlarge the power conferred by the Act. The phrase "on the basis" was read consistently with section 12(2), which also requires assessment on a correct and complete return. The provisional assessment made outside these limits was without competence and was set aside.

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Issues: Whether, in making a provisional assessment under section 5(8) of the Mysore Sales Tax Act, 1957, the assessing authority could discard the dealer's estimate and the previous year's turnover and instead make a best judgment assessment under rule 16(b).

Analysis: Section 5(8) permits advance assessment only on the basis of the estimate furnished by the dealer or on the basis of the dealer's transactions in the previous year. The authority must choose one of those statutory bases and cannot resort to any other material for a provisional determination. Rule 16(b), insofar as it authorises a best judgment estimate for provisional assessment, enlarges the power conferred by section 5(8) and is repugnant to the Act. The expression "on the basis" in section 5(8) was read consistently with section 12(2), which requires final assessment on the basis of a correct and complete return.

Conclusion: The provisional assessment made by the authority was without competence and was set aside.

Ratio Decidendi: Where a statute prescribes specific bases for provisional assessment, the assessing authority cannot substitute a best judgment assessment under delegated rules that enlarge the statutory power.

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