I guess my question has to deal with my ex husband not taking responsibility for my children. He sees them when it is convenient for him and has hardly paid any child support since we were separated about a year ago. What are the rules for filing abandonment charges on him in the state of Indiana?

Not really any. You take him back to court to force him to pay support, ask the courts for a garnishment of his wages for child support.

None. Child abandonment is leaving a child unattended. Since he hasn't done that there is nothing to charge him with.

If there is a support order in place, you can go back to the courts to enforce that order.

But you can't force him to visit or contact the kids.

Ok as already said you can't file charges against him since he didn't abandon the children by Indiana law. What you do is go back to court to have the support order enforced.