Includes "alternative minimum tax" (AMT), starting with 2000. For previous years, AMT was excluded and was reflected only in "total income tax".
For additional information about the return filing requirements, see the annual reports, Statistics of Income-Individual Income Tax Returns at https://www.irs.gov/uac/soi-tax-stats-historical-data-tables.
U.S. Department of the Treasury. Internal Revenue Service, Individual Income Tax Filing: Income Tax After Credits [INCTACDT], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/INCTACDT, October 26, 2020.