Innovating two complementary income tax Schedules and Forecasting the Undiscovered Personal Income Tax Revenue Abstract A general problem in today’s Ethiopia is the failure or unwillingness to discover income tax base for a period of Pagume. The non existence of income tax base for Pagume means that there is neither factors income of scarce resources . (salary income to labor, house rent income to the owner of capital building, profit to entrepreneur) nor income tax revenue from the source side. Therefore, in terms of both short run and long run periods, the personal income tax revenue of Pagume remains undiscovered. Because the current income tax schedules do only cover income tax base of common period (360 days=12 months times 30 days).Common period means only the period of 360 days that is less than the universal period of year by the number of days of Pagume. Universal period is a period of year that covers 365 or 366 days once in a leap year. Nevertheless, the current income tax law verbally directs every employer how to treat the income tax base of Pagume. “Employers have an obligation to withhold the tax from each payment to an employee, and to pay the withheld amounts to the Tax Authority the amount withheld during each calendar month, in applying preceding income attributable to the months of Nehase and Pagume shall be aggregated and treated as the income of one month.” Income tax law (1994) at 1873 Moreover, according to the above rule, if there is factor income during Pagume, the serious problem is that there are no two complementary income tax schedules available for the accounting department of any budgetary institute that use to estimate, legislate, execute and audit income tax bases of Nehase and Pagume. This means that the economics of Pagume is undiscovered. To discover the undiscovered economics of Pagume, the study makes new income tax theories such that “broadening income tax bases yield more tax revenue to the government and disposable income to the tax payer”. Besides, to translate these new income tax theories into practice, two complementary income tax schedules are innovated for the special period of 35 and 36 days. The research addresses concepts of universal fiscal year and income tax period. Ethiopia’s fiscal year or income tax period has a set of 12 months: 11 of 30 days and one special month of 35 and 36 days once in a leap year. Tax work is too technical and specialized. Therefore, operational concepts such as income tax brackets, optimum taxable income, marginal tax, total income tax revenue, average income tax and disposable income are explained. To innovate two complementary income tax schedules for the special period of 35 and 36 days, the study multiplied the current income tax schedule by factors 1.1667(=35/30) and 1.2(=36/30) respectively. This exercise results in the first and second complementary income tax schedules. The first complements the common income tax schedule when t