An ITIN (Individual Taxpayer Identification Number) is a 9-digit tax number from the IRS (the US tax office). It starts with 9. It is for people who must deal with US taxes but cannot get a Social Security number.
It does not give permission to work, and it does not change your immigration status.
A spouse or child listed on a family tax return, for example an H-4 spouse without an EAD, or an F-2 or J-2 family member.
A person with US income who cannot get an SSN.
Some people who need to claim a tax treaty benefit.
If you can get an SSN, you should not get an ITIN.
Fill in Form W-7 (from irs.gov) for each person.
Attach it to the front of the federal tax return (Form 1040 or 1040-NR). Most people apply in tax season (January to April) with the return. Leave the SSN box blank for that person.
Add proof of identity and foreign status. A valid passport is the only document that proves both by itself. Otherwise you need two or more other documents (for example a national ID card and a birth certificate). Dependents may need proof they live in the US, such as school records.
Send it in one of three ways:
By mail to the IRS in Austin, Texas, with original or certified copies of your documents. The IRS returns originals by mail, which can take weeks.
Through a Certifying Acceptance Agent (CAA). They check your passport and send copies, so you keep your originals. They charge a fee.
At an IRS Taxpayer Assistance Center with ITIN service. Free, by appointment, which may take weeks to get.
Allow 7 weeks. In tax season (January 15 to April 30) or from abroad, allow 9 to 11 weeks.
An ITIN expires if it is not used on a federal tax return for three tax years in a row. You then renew with a new W-7.
Mailing your only passport. Use a CAA or IRS office if you need your passport.
Applying without a tax return, when no exception applies.
Paying a company that "guarantees" a fast ITIN. The IRS process is the same.
Keeping the ITIN after you get an SSN. Tell the IRS so your records combine.