Form W-7 is used to apply for a USTAXID or often referred to as ITIN [Individual Tax Identification Number], This application process is required for non-citizens who aren’t eligible to receive a Social Security number but need to file a federal tax return with the IRS for income from US sources. A common scenario includes a foreign person with a United States based income filing a 1040Nonresident Federal Tax Return or US citizen/resident alien with a foreign spouse filing a joint 1040 tax return with a Married filing Jointly status.