My 7 year old, who I have full custody of, was claimed by his father on income tax w/o my permission. He had abandoned our son for 5 years & recently obtained visitation. He does not comply. He was ordered 2 pay child support, he does not comply, but he claimed my son. How do I go about rectifying this & also preventing this from happening again?

You file and claim the child, you will have to have done this with paper return most likely if he filed first listing

This will not stop him from doing it again, but it will be him that will have to repay money he got refunded incorrectly.