An incorrect or missing SSN can increase your tax or reduce your refund. To apply for an SSN, fill in Form SS-5 and return it, along with the appropriate evidence documents, to the Social Security Administration (SSA). You can get Form SS-5 online at www.socialsecurity.gov,
from your local SSA office, or by calling the SSA at 1-800-772-1213. It usually takes about 2 weeks to get an SSN once the SSA has all the evidence and information it needs.
Check that your SSN on your Forms W-2 and 1099 agrees with your social security card. If not, see page 4 for more details.taxmap/instr/i1040ez-009.htm#TXMP1170010f
If you are a nonresident or resident alien and you do not have and are not eligible to get an SSN, you must apply for an ITIN. For details on how to do so, see Form W-7 and its instructions. It usually takes about 4–6 weeks to get an ITIN.
If you already have an ITIN, enter it wherever your SSN is requested on your tax return.
An ITIN is for tax use only. It does not entitle you to social security benefits or change your employment or immigration status under U.S. law.
If your spouse is a nonresident alien, he or she must have either an SSN or an ITIN.