I legally changed my first name so my W-2 but it does not match my SS card, is that legal?

No, the ss# is what they key on.

Yes, this is going to cause a problem for you. You need to notify the Social Security Administration that you have legally changed your name and get a new social security card. That way, when you file your tax return, the new name you list on the tax return at the IRS will match the Social Security Office Records. Also, you should attach a copy of the court order changing your name to your tax return.

You should apply for a new social security card from SSA with your new legal name. You should send a certified copy of the court order along with your application.

The only thing that the I.R.S. requires is that your name as it appears on your tax return matches your name as it appears in the SSA database. This is due to the fact that your social security number is tied to your previous legal name, and the I.R.S. extensively uses social security numbers to identify taxpayers. Until you change your name with the SSA, you should use your previous legal name on your tax returns. Otherwise, they'll have a problem matching your new name with your social security number, and the return will be rejected or flagged for review.

No. You might want to let IRS know that both names are you.