Another confusing form W9 term deals with backup withholding. Virtually every taxpayer can say they are not required to have backup withholding. When someone is required to have backup withholding, they are notified by the IRS. This means that 28 percent of income, even self-employment income, is held from their checks at IRS order. This applies to people who owe back taxes. In addition, the IRS can require backup withholding when the information on form W9 appears incorrect. If your name and Social Security Number do not match, then the IRS will likely order 28 percent of your self-employment income held until the situation is rectified. Common misspellings and marriage name changes can easily lead to mistaken backup withholding, so it is especially important to fill out a W9 form accurately and print clearly to avoid any misunderstandings.