What about the non-US citizen married to a US citizen both living in Europe and not earning income in the US? Does the non-US citizen need to file for US taxes when he has no US income nor is a US citizen?

Would the US citizen spouse should just file in married filing separately?

The U.S. citizen can file by herself as Married Filing Separately. She would identify her spouse by name on the return and put "NRA" (for Non-Resident Alien) where his SSN would go. This return would have to be mailed.

OR

The couple can file a joint return and the non-U.S. citizen would sign a statement CHOOSING to be treated as a resident alien for all of 2010.

Those are the two options available. There is not enough information provided to determine WHICH option is the best course of action tax-wise.

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