I'm not at all sure of what you think he may do to you. I would be a little more concerned with what the IRS would do. If you lived together until very recently you may be legally able to file jointly. It would certainly be to your advantage to check the regulations concerning whether you can even file jointly. If you are still in school you may be able to ask some of the teachers in the business department (an accountant should know the time element here). Another thing you can do is call the IRS and ask them. They have a toll free line, just be patient as you may be on hold for a long time. Even if you sent him a copy of your W-2 you would still have to sign the return. If someone else signs for you - if they do it is forgery and forgery may be grounds for a prison sentence. My "gut" reaction is that you are now single and you should act that way and this includes such issues as taxes.

If you were divorced as of December 31, 2011, then you no longer have the choice of filing your taxes jointly. Your options are Single or Head of Household (if you qualify).

He's most likely going to owe if he was having his withholding done as married with a child all year and he has to file as single. I have a feeling he's worried about his own tax bill if he has no spouse or dependents to claim.

If you were divorced after December 31st and you lived apart for the last six moths of 2011, you can still file as head of household without him if your child lived with you.