I have recently tried to file my taxes electronically as usual and was rejected twice because apparently someone else has used my recently fifteen month old deceased daughter on their tax return as their dependent. Now, the first and only time she was used as a dependent was just last year by me and it was accepted, but this time I have this issue. So my question is, outside of sending a paper return to the IRS for this long drawn out charade, what steps must I take to insure that this individual is brought to proper justice for engaging in this disrespectful, fraudulent act?

First make sure it wasn't something you did last time you filed. What date did she die?
Second, is there an ex in the picture?
Third, I take it she didn't have a SSN?

It's possible that there is a bug in the e-file software, I suppose. Try not to think yet in terms of some horrible person doing this, unless it's an ex, because how would someone else identify your child?

If you have an IRS office nearby or can stand to wait on the phone, contact them. They won't reveal who (if anyone really did) claimed her, but they might be able to shed some light on this.

From reading other posts on this subject I think it's a bug in efile. If that's true, you are awful, IRS, shame on you. As if parents haven't been through enough.

Many things, there are people who try and steal ID of children who die for various reasons, but no there is no quick fix, you are going to have to do a paper return and explain that someone has used this ID improperly.
Do not expect any "justice" or any "fix" other than you getting your return done after many months of review.