Fathers who were legally married to the child's mother at the time of the child's birth are the child's presumed father. They are entitled to visitation and child custody if the parents divorce, and they must pay child support if they no longer live with the child. This paternity, however, may be challenged if another man asserts that he is the father of the child, and he undergoes a paternity test. However, fathers may still be obligated to support their children if they acted as the child's father for an extended period of time. States are influenced by the child's best interests when making paternity decisions, and it is often not in the child's best interests to remove a father from her life.
Unmarried fathers are not legally acknowledged as the child's father until they or the mother petition the court to acknowledge him as the father. State procedures vary slightly, but typical requirements may include obtaining a paternity test or signing documentation, along with the mother, that the father acknowledges his paternity. After a father becomes the child's legal father, he may be obligated to pay child support and entitled to custody or visitation with the child. Men should not sign voluntary acknowledgments unless they are certain they are the child's father, because it is difficult to be removed as the legal father once you have signed such documentation.
After a father has been established as the child's legal father, he may only disprove paternity by taking a paternity test or when another man takes a paternity test demonstrating that he is the biological father. In some states, the legal father may then petition the court to be removed as the child's legal father. Some states allow legal fathers to disprove paternity at any time; others only allow it while a child is still a baby. And in some states, men may not attempt to disprove paternity at all, and the only way to disprove paternity is via a paternity claim from another man. In many cases, however, if the father has served as the child's parent for several years, the court may still classify him as the child's legal father. If there is not another father willing to fill the role or if removing the father is not in the best interests of the child, non-biological fathers may still be classified as legal fathers, obligating them to pay child support. This is why it is important to be absolutely certain the child is yours before signing a birth certificate or signing a stipulation to paternity.
Paternity fraud, which occurs when a mother tricks a man into believing he is a child's father, is extremely difficult to prove. It is not sufficient simply to prove that the man is not the child's biological father. Instead, the accuser must demonstrate that the mother knowingly and willingly misled the father. Some states, such as Florida and Iowa, permit men to sue for paternity fraud to recover back child support payments and other payments made to the mother or the child.