Can you file even if you don't know your spouse's SSN or ITIN?

You would list a resident-alien spouse on your return and provide his or her Social Security number (SSN). If your spouse is not eligible for a Social Security number, they will need to apply for an Individual Taxpayer Identification Number (ITIN) from the IRS.

If your spouse is a nonresident alien, you can treat your spouse as a resident alien for tax purposes. If you choose this option, you can file a joint tax return with your spouse and have an increased standard deduction. You increase your standard deduction, but all your spouse's worldwide income will be taxed by the United States. 

If you do not choose this option you may be able to use the head of household filing status as long as you have paid more than half the cost of maintaining a household for certain dependents or relatives other than your nonresident alien spouse.

Under U.S. federal tax law, you cannot file your taxes as a single person once you are married. This is true even if your spouse is not a U.S. citizen. After you get married, you can only choose between filing under the following three statuses:

• Married Filing Separately
• Married Filing Jointly
• Head of Household.

If your spouse is a nonresident alien, the automatic filing status is Married Filing Separately unless you choose to change it.

Please note that even if your spouse lives in a different country, you are still not allowed to file your taxes as a single person in the United States.

If you want to file as Married Filing Jointly and your spouse is a nonresident alien, you can follow the steps outlined below:

1. Your spouse must apply for an ITIN (Individual Taxpayer Identification Number) from IRS
2. Attach a declaration to your tax return (as a resident alien or U.S. citizen) that your spouse is a nonresident alien, but they choose to be treated by the IRS as a resident alien. Both of you must sign this letter.
3. On your joint tax return form, include your spouse’s name, address, and ITIN (in place of an SSN).

After you file a joint tax return in this way, the IRS will continue to treat your spouse as a resident alien for tax purposes every year until you change your decision and tell them in writing.

The IRS does not allow electronic filing of returns without a SSN or ITIN. Sign in to your eFile.com account and start a tax return and complete the Name & Address page. Enter your information. In order for your to be able to prepare a return, you will need a temporary SSN for your spouse or applicant for the ITIN.