The database provides data on Internal Revenue gross collections by type of tax.  Numbers are in current dollars, reflect gross collections, and are rounded.

• Partnership and S corporation data are not shown in this table since they generally have no tax liabilities.
• Beginning with Fiscal Year 2009, Total income tax excludes credits to taxpayer accounts.
• Total collections include taxes on corporation income (Form 1120 series) and unrelated business income from tax-exempt organizations (Form 990–T).
• Business income taxes reported for estates and trusts are included in individual income tax in Fiscal Years 1960–2007.  Beginning with Fiscal Year 2008, estate and trust income tax is reported separately.
• Individual income taxes include taxes for Old-Age, Survivors, Disability, and Hospital Insurance (OASDHI); unemployment insurance under the Federal Unemployment Tax Act (FUTA); and railroad retirement under the Railroad Retirement Tax Act (RRTA).    
• Estate and trust income taxes exclude excise taxes collected by the U.S. Customs and Border Protection and the Alcohol and Tobacco Tax and Trade Bureau. The Internal Revenue Service collected taxes on alcohol and tobacco until Fiscal Year 1988, and taxes on firearms until Fiscal Year 1991.
• Employment taxes represent fiscal-year transitional period, July 1976 through September 1976, resulting from redefinition of the term “fiscal year.” Fiscal Year 1976 covered July 1975 through June 1976 (earlier years were similarly defined). Fiscal Year 1977 covered October 1976 through September 1977 (subsequent years are similarly defined).
• The estate tax was temporarily repealed for deaths in Calendar Year 2010 before being reinstated retroactively with a $5-million exemption as part of the Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010. As a result of this legislation, the estates of 2010 decedents could elect to file either Form 706 (estate and generation-skipping transfer tax return), due September 19, 2011, or Form 8939 (allocation of increase in basis for property acquired from a decedent), due January 17, 2012. The law also provided a $5-million exemption for the estates of 2011 decedents. These tax law changes significantly reduced estate tax gross collections in Fiscal Year 2011 relative to other fiscal years.
•  Gift taxes are based on the Federal tax law in effect for the year in which they are given, and the majority of gifts given in one year are reported to the IRS in the following year. Gift tax collections decreased significantly between Fiscal Years 2011 and 2012, which reflects a decrease in the amount of gift tax collections on gifts made primarily in 2010 and 2011. Gifts made during Calendar Year 2010 were subject to a maximum unified credit amount of $330,800; gifts made during Calendar Year 2011 were subject to a maximum unified credit amount of $1,730,800. The unified credit, which applies to the sum of both taxable gifts made during life and a decedent’s estate, is a credit to offset the amount of transfer tax that would be assessed on assets below the applicable exclusion amount.

For additional information on categories, see Detailed IRS Collections.