My husband has a child from a previous marriage. The child has lived with her father from the time of the divorce until her 17 th birthday (a little over 3 yrs). My husband has never asked for child support. Only that the mother pay half the medical bills and school needs (lunches/school supplies). Shortly after her 17th birthday, her mother informed her that she could choose where she lived. The Mother and Step Father came to our home while we were at work, and removed her form our home. They are asking for child support and refuse to let my husband have time with his daughter.
We have spoke to his attorney. She just says he's a nice guy and he did not ask for it. I need to know can he ask for back child supprt this late in the game?

No he can't since he never filed. He could make it a point that she lived with him for the past three years and never got a dime. He could file for primary custody to try to get her back. What state arebyou in? In some states once the child turns 18 they are no longer eligible for support unless maybe they go to college.

Was the father's custody ordered by a court? If so, then they can't change custody until they modify the court order or she turns 18.

Since he chose not to ask for support, he can't change his mind now. However, I have doubts that a court will order support at this juncture.

Once this gets to court, the father should present evidence that he has supported his daughter for the last three years. I think the court will order nothing more than the same arrangement they had, where he pays half the medical bills and school costs.

As for not letting him have time with his daughter. He needs to document this and get the court to order visitation. If the court sees that the mother has been withholding time, they will not look kindly on the mother.

Now, I'm going to add a caveat here. It would appear the daughter may have wanted to get away from her father. That fact that she seems to have gone willingly and has not tried to contact him (there are multiple ways she could get in contact without the mother knowing) there could be something more going on here than you have told us (or are aware of). I don't know what that would be, but it does seem strange that a 17 yr old would just want to change custodial parents at this point.

At the divorce, there should have been child custody order. The child can not just decide where they want to live. The child has to live where the court order says.

No in most places you can not file for back support, you needed to file for that, when you got child.