Presidential Allowance Modernization Act of 2019 This bill replaces provisions governing the compensation provided to a former President. Each former President shall receive from the United States (1) an annuity of $200,000 per year for the remainder of his or her life, and (2) a monetary allowance of $200,000 per year. Such allowance shall be reduced by the amount the former President's earned income exceeds $400,000. These monetary amounts are subject to a cost-of-living increase. The widow or widower of each former President shall be entitled to receive from the United States a monetary allowance at a rate of $100,000 per year, payable monthly by the Department of the Treasury, if such widow or widower waives the right to each other annuity or pension to which she or he is entitled under any other Act of Congress. This is prospective to future Presidents who have not yet held office.