A W-7 form is an IRS form noncitizens use to apply for an individual taxpayer identification number when they are ineligible for a Social Security number, explains Turbo Tax. This number is required for a federal tax return to report income from U.S. sources.
A W-7 form asks for the reason the applicant needs an ITIN and the applicant's name, mailing address and foreign address, the date and location of birth and the country of citizenship, states Turbo Tax. The applicant also must provide his foreign tax identification number, U.S. visa number and other details to verify identity. ITIN's also are required for spouses and children of noncitizen taxpayers.