The Illinois Affidavit of Biological Parent is a legal document used to establish paternity in the state of Illinois. It is typically used when the biological father of a child is not listed on the birth certificate, or when a father wishes to establish legal parental rights. There are two types of Illinois Affidavit of Biological Parent. The first is a Voluntary Acknowledgement of Paternity, which is a voluntary agreement between the biological parents to establish paternity. The second is a Court Order of Paternity, which is an order issued by a judge in a court of law to establish paternity. Both types of affidavit require the signature of the mother, father, and any witnesses, as well as notarization or court approval.