**IV-D ("4-D"):** Refers to title IV-D of the Social Security Act, which says that each state must create a program to find noncustodial parents, establish parentage, establish and enforce child support obligations, and collect and distribute support payments. Any person that gets public assistance (usually TANF) is referred to the state IV-D child support program. States must also accept applications from families that do not get public assistance, if requested, to help collect child support.