Quarterly Installment Tax Calculator - Version QITC Calculate your current or last year's quarterly installments, as they come due using the Annualized Income method. Also, since it computes the current year's full IRS 1040, displaying all the lines of the 6251, Sched. D, A, 1040 and many of the Credits and Worksheets, this program is ideal for what-if situations involving ISOs, AMT, TMT, high-income and credit limitations and phaseouts