Advance tax underestimation expands liability where it reduces the first two instalments, tightening advance-payment compliance obligations.

The amendment substitutes clause (a) to treat an underestimation of advance tax payable under the advance-payment subsections as operative where that underestimation thereby reduces the amount payable in either of the first two instalments, thereby extending the clause's application to underestimates arising under the specified advance-tax provisions.

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