A taxpayer completes a W-9 tax form by entering his full legal name on the first line, the name of his business on the second line if necessary, tax classification and Social Security number, according to TurboTax. The W-9 form is submitted to an employer rather than the IRS.
Taxpayers use the W-9 tax form to give their tax identification or Social Security numbers to employers or individuals who must report to the IRS any income they pay a taxpayer, notes the IRS. Examples of items that have to be reported to the IRS on an information return, besides income, include real estate transactions, cancellation of a debt, paid mortgage interest, IRA contributions, and abandonment or acquisition of a secured property.
Nonresident aliens in the United States who don't have a Social Security number have to use a taxpayer identification number when completing a W-9, according to TurboTax. Those who have an employer identification number because they operate their own businesses should use that number on the W-9 form in the EIN space.
There are cases where the IRS requires the company or individual asking for a W-9 form to withhold a portion of the taxpayer's income, which is known as backup withholding, notes TurboTax. A taxpayer is notified before a portion of his wages is withheld.