Interest on advance tax shortfall accrues from April until application, order or reassessment, including Settlement Commission adjustments. The amendment requires assessees who file settlement applications to pay simple interest at the prescribed monthly rate on additional tax from the first day of April of the assessment year until the application date; where a settlement order increases disclosed income, interest runs from the first day of April until the order date on the tax difference, and any subsequent settlement variation adjusts interest. It substitutes the reassessment/recomputation provision to impose simple interest from the first day of April following the financial year until reassessment or recomputation on the increase in tax determined, and omits a prior textual reference to settlement orders in the related subsection.