Originally Posted by Wnhough

you need to complete Form W-7 only if the Social Security Administration notifies you that a SSN cannot be issued. By law, an alien individual cannot have both an ITIN and a SSN. You should complete Form W-7 as soon as you are ready to file your federal income tax return, since you need to attach the return to your application. You can call the IRS toll-free at 1-800-829-1040 if you are in the United States. If you are outside the United States, call 267-941-1000 (not a toll-free number) for information and help in completing your Form W-7.
https://www.irs.gov/pub/irs-pdf/fw7.pdf
https://www.irs.gov/forms-pubs/about-form-w7



As you know, ITINs are for federal tax reporting only, and are not intended to serve any other purpose. IRS issues ITINs to help individuals comply with the U.S. tax laws, and to provide a means to efficiently process and account for tax returns and payments for those not eligible for Social Security Numbers. An ITIN does not: authorize work in the U.S. Provide eligibility for Social Security benefits;qualify a dependent for Earned Income Tax Credit Purposes.