Child support enforcement cannot begin until paternity is established, but one-third of children on welfare have no legal father. The Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA) requires states to show progress toward establishing paternity for 90 percent of the children on their caseload who need to have paternity established or for 90 percent of all births outside marriage; if they cannot do so, states will have to pay financial penalties. Welfare reform also extends the legal status of voluntary paternity acknowledgments. For example, after a father voluntarily signs a paternity acknowledgment and 60 days have passed, he cannot rescind it unless he can prove fraud, duress, or material mistake of fact. Fathers in a contested paternity action are denied the right to a jury trial (of any kind).

Initially, the burden of proof is on the woman to prove that the man she is asserts to be the father is the biological father of her child. In order to shift the burden of proof from the mother to the alleged father, various jurisdictions typically require: