When you are married, you must either file a joint return with your spouse or a separate return alone. (One exception, if you were separated for the whole year and have a dependent, you may be able to file as head of household or single.) If you are filing separate and had community income while you were living together, then half of your earnings go on his return, and half on yours. That's why they need to know your earnings, and you need to know his. Some couples agree to each report their own earnings, withholding, etc.
Answered on Mar 31st, 2013 at 10:41 PM