First, if you are married on 31 December 2010, the IRS considers you married for the ENTIRE year.
As for HOW to file, you can file Married Filing Separately, in which case your spouse does NOT need a SSN or ITIN. You simply enter his name and MANUALLY print the words "Non-Resident Alien) where his SSN would go. By filing this way, you CANNOT file electronically; the return MUST be mailed.
Now, you CAN file jointly with your husband, reporting ALL world-wide income for BOTH of you and using a combination of the Earned Income Exclusion (Form 2555) and the Foreign Tax Credit (Form 1116) to avoid double taxation. This method would require your husband to complete and sign a Form W-7 to request an Individual Tax Identification Number (ITIN). He would staple a notarized photocopy of his passport to the W-7, then paper clip both documents to the joiont tax return, which you BOTH would sign. He also need to sign a statement that he CHOOSES to be treated as a resident alien for all of 2010.
Due to the Form W-7, this return must be mailed as well.
You would need to model the returns BOTH ways to determine which is the best course of action tax-wise.
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