I was misinformed by an online tax application that my wife and I would save $ if we filed separate federal returns and a joint state return.

The state accepted our return, but now says we must file separated like the federal.

Looks like the joint federal / joint state works out better.

Q: How do we go about changing the individual federal returns into one joint return?

John

You need to submit Form 1040X to amend your return to file jointly. Attach a properly-prepared Form 1040 with the Form 1040X and have you and your wife sign BOTH the Forms 1040 AND 1040X.