My name is on my mortgage, but my fiance's name is also on the deed. We pay equally. Do I need to fill out a Form 1040, or can I just divide the interest on my 1098?

I believe my fiance is supposed to file a Form 1040, but I just don't know if I'm supposed to do that as well. All of the articles I've seen about it are from the person on the deed's point of view, not the person on the mortgage's point of view.