The CSA requires proof that a paying parent is a biological or adoptive parent of a child. Proof could be the parents name on the child’s birth certificate. The CSA will only issue a child support assessment to a person if proof can be provided that the paying parent is a biological or adoptive parent of the child.
If you cannot provide acceptable proof, you may need to take court action and have DNA testing done. Seek legal advice if you need proof of parentage.