Your daughter's father is likely going to have tax problems, but those should not be your problems. I think you should focus on the child support. If you have a court order for support, then you should enforce it. For help, you can refer to a good general resource at --
The IRS might help enforce child support payments (there are applicable laws), but if the IRS does not know about the support order, or if your daughter's father is hiding income, the IRS might not know about any money available.
You can look for help to many local law firms (my own included, or you can seek help at the U of U clinic -- http://www.law.utah.edu/probono/free-legal-clinics/
You may also want to talk with the people at Utah's ORS -- http://www.ors.utah.gov/index.html
This answer or response should not be considered legal advice, and does not create an attorney-client relationship. If you have further questions, I would be glad to discuss your situation further. I can be reached at US - (801) 746-6300, or online at -- http://www.lewishansen.com/attorneys/robinson.html