Alternative Fuel Tax Credit Extension Act of 2019 This bill extends and phases out the tax credit for alternative fuels used as a motor fuel, including compressed, liquefied, and renewable natural gas. It provides for a credit equal to the product of (1) 50 cents and the number of gallons of alternative fuel used in certain vehicles before January 1, 2025, and (2) 25 cents for 2025 through 2026. The credit terminates after 2026. The bill also extends outlay payments of such credit through 2026.