The Individual Taxpayer Identification Number [ITIN] is a U.S. taxpayer identification number, issued by the Internal Revenue Service [IRS]. It is for individuals who are required to have a taxpayer identification number for tax purposes, but who do not have and are not eligible to obtain a Social Security Number [SSN] from the Social Security Administration.
If you are required to have a federal tax identification number (or file a federal income tax return), and you are not eligible to get a SSN, you must apply for an ITIN.
Update 9/26/2017: Due to changes in IRS processing of ITIN applications, you must plan to apply for your ITIN by mail, or in person with a Certified Acceptance Agent, or Acceptance Agent. Please follow the updated instructions below.
You can apply for your ITIN in one of two ways, by mail, or in-person. Determine which option will work best for you, and review the submission instructions here.
ITIN Processing with the IRS
You will receive a letter from the IRS assigning your ITIN within 4-6 weeks. If you have not received your ITIN or other correspondence six weeks after applying, call the IRS toll-free number at 1-800-829-1040 to request the status of your application if you are in the United States.