Source: U.S. Department of the Treasury. Internal Revenue Service  

Release: SOI Tax Stats - Historical Data Tables  

Units:  Number of Returns, Not Seasonally Adjusted

Frequency:  Annual

Represents tax withheld on (a) salaries and wages; (b) certain tip income; (c) pensions and annuities; (d) certain gambling winnings; and (e) distributions from profit-sharing plans, retirement plans, and Individual Retirement Arrangements (IRAs). Also included are taxes withheld as a result of "backup withholding" on certain interest, dividends, and royalty payments, which otherwise were not subject to withholding.

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.