A taxpayer identification number must be furnished on all returns, statements, and other tax–related documents and must be given upon request to any other person who must include it on a return or statement. For most individuals this is a Social Security Number, or SSN. If you are a foreign person who does not have and is not eligible to get an SSN, you must use an Individual Taxpayer Identification Number, or ITIN.

You need an ITIN if you are:

A non-resident alien individual eligible to obtain the benefits of a reduced rate of withholding under an income tax treaty,

An alien required to file a U.S. tax return or filing a U.S. tax return only to claim a refund,

A nonresident alien electing to file a joint tax return with a spouse who is a U.S. citizen or resident,

Claimed as a spouse for an exemption on a U.S. tax return, or

Claimed as a dependent on another person's U.S. tax return.

The ITIN is issued for federal tax purposes only. It does not entitle you to Social Security benefits, and does not make you eligible for the earned income credit. The ITIN creates no inference concerning your immigration status or your right to work in the United States.

You must file Form W-7(PDF) , Application for Individual Taxpayer Identification Number, to apply for an ITIN, and show that you have a federal tax purpose for seeking the ITIN. In most cases, this will require attaching a federal tax return to the most current revision dated 12–17–2003 of the Form W–7. Along with the completed Form W-7, you will submit identity documents, and either a federal tax return, or other documentation to show the federal tax purpose for which you need the ITIN.

The identity documents are needed to verify both your identity and your foreign status; one must include a recent photograph. If you submit an original valid passport (or a notarized or certified copy of a valid passport) you do not need to submit any other documents. If you do not submit a passport document, you must provide a combination of documents (at least two or more) that are current and that (1) verify your identity (that is, contain your name and a photograph), and (2) support your claim of foreign status.

If the ITIN is for a dependent, the documentation must prove that the dependent lives in the United States, Mexico, or Canada. If the dependent is a minor, the documentation must establish the relationship between the dependent and the representative signing the application on the dependent's behalf. Such documentation could include a birth certificate, adoption papers, or other court-appointed papers showing legal guardianship.

In addition to a passport, examples of acceptable documentation include: national identification card (showing photo, name, current address, date of birth and expiration date); civil birth certificate; foreign driver's license; or visa. A complete list of acceptable documentation can be found in the instructions to the Form W-7. The documents must be originals or certified copies.

You can apply for your ITIN by mail or in person at most IRS offices in the United States. If you apply in person, your documents will be reviewed and returned to you. Publication 1915(PDF), Understanding Your IRS Individual Taxpayer Identification Number, has a list of IRS offices abroad which can accept Form W–7. If you apply by mail, use the address shown in the Form W–7 instructions and in Publication 1915. After reviewing your application, your documents will be returned to you. If your original documents have not been returned within 60 days, you may call 1–800–829–1040 (in the United States), or 1–215–516–2000 (outside the United States), to find out about the status of your documents. It takes approximately 4 to 6 weeks for the IRS to notify you in writing of your ITIN.

For more information, refer to Publication 1915. You may also want to obtain Publication 519, U.S. Tax Guide for Aliens. For information about who qualifies to be claimed as a dependent, refer to Topic 354.