If the father is married to the child’s mother, Florida law presumes that he is the child’s legal father and he is responsible for child support, even if he is not the child’s biological father. He can stop this obligation by filing a Petition to Disestablish Paternity. If the father is not married to the child’s mother, he is not recognized as the legal father until he voluntarily agrees to paternity or it is done by an administrative or court order. He will not have any child support obligation until paternity is established. However, he may be responsible for up to two years of back child support, from the date paternity is proven.