Sure, you thought that DNA test would prove paternity once and for all right? Wrong. When unmarried couples bear children, the father is not automatically entitled to have his name on the birth certificate. A father can have his name on the birth certificate simply by proving though a paternity action he is the biological father. A father can also have his name placed on the birth certificate if he signs a written acknowledgement of paternity. You can acknowledge paternity even if you are not the biological father.
This signed acknowledgement of paternity can be challenged within 60 days. After 60 days, a signed acknowledgement of paternity can be challenged only on the basis of fraud, duress or material mistake of fact. If a man signs an acknowledgement of paternity then that man can become liable for child support even if he is not the biological father.
If you say you are the father in writing, it may be very difficult to avoid paying child support later on even if DNA evidence proves otherwise. This is because a signed acknowledgement of paternity is extremely difficult to set aside after 60 days.