Paternity is legal fatherhood—and establishing it is one of the most important steps in the child custody and support processes. A man is generally presumed to be the father of children born to his wife during their marriage. For unmarried parents, the biological father does not have legal rights to his child until paternity is established. Paternity may be established through a court-ordered paternity test, or by the father signing an acknowledgment of paternity (AOP).

In a case of mistaken paternity, a man who believes he is not the father of the child may file a petition (lawsuit), and the court may generally terminate the parent-child relationship and the man’s obligation to pay child support upon proof through genetic testing that he is not the father of the child.

The process of adding a father to a birth certificate is an important issue related to paternity.

In Indiana, paternity establishes legal fatherhood, which is crucial for child custody and support matters. When a child is born to a married couple, the husband is presumed to be the father. For children born to unmarried parents, the biological father has no legal rights until paternity is established. Paternity can be confirmed either by the father signing a voluntary Acknowledgment of Paternity (AOP) form or through a court-ordered DNA test. If a man has reason to believe he is not the biological father of a child for whom he has been identified as the father, he can file a petition to challenge paternity. The court may terminate his parental rights and obligations, such as child support, if genetic testing proves he is not the biological father. The process of adding a father's name to a birth certificate is directly tied to the establishment of paternity and can be done voluntarily at the time of birth or after paternity has been legally determined.