I was recently asked if an adult child could go back after their father for child support even though they are now an adult. Their mother never wanted to but she had died and the adult child (who was 45) wanted to try to make their father pay child support for all of those years. I also had a similar question from a 23 year old who just found out who her biological father was and wanted to know if he could be adjudicated as her father. Both of these adult children wanted to know if they could collect past child support.
In Wisconsin, the law is clear that a paternity action must be commenced prior to a child’s 19th birthday. Child support typically commences from the date of service of a valid legal paternity action or an adjudication of paternity.
Also in Wisconsin, the court cannot order retroactive child support, whether in a paternity or divorce case. The soonest the court can order or modify child support is from the date of service of a valid action or a motion. In other words, under the scenarios above, neither of those adult children could obtain the relief they wanted to under the laws of the State of Wisconsin nor could their father be ordered to pay past support.
If, on the other hand, there had been an order for child support entered while the child was a minor that had never been paid by responsible parent, that order can be enforced and the past due support collected for up to 20 years after the termination date of the child support order. In addition, in the aforementioned situation, the person looking to collect past child support can also convert an arrears (past-due child support) order to a money judgment after the date the child reaches the age of majority to give him or her more options for collecting.
Wisconsin Family Law Info 
In a paternity case, for an adult child he’s paid child support for, what would paternity-post adjunction be? I’m confused as to why after 26 years this is in court.
Without knowing all of the facts or reviewing the paperwork, I would have no idea. You should consult with an experienced family law attorney to review to determine what is going on and what you need to do. Good luck.
I dated this girl back in 1996 (I was 18 or 19) in Wisconsin and she took me to court for child support. I showed up in court not knowing anything but wanting to have a paternity test done cause I honestly never thought the child was mine, The mother Never showed and it was postponed. I show up again and she failed to show again and the judge looked at the attorney and asked where she was and he replied he didn’t know and it was postponed again, I showed again for the third time and she never showed and the case was dismissed. This girl literally disappeared…. 30 yrs later this girl contacts me via FaceBook and asked questions and we finally done a paternity test and she was my daughter the whole time. Her Mother lied to her until she was 17. And to this day I am trying to clear my name to my daughter to prove I showed up… Can that be proven anyhow? Can she come after me for support?
You can contact the county in which the paternity case was filed to see if you can get a copy of the file. They may or may not still have it. Or, they may have some kind of notes on the computer. That is probably about the only thing you can do. To answer your second question, no, she can no longer come after you for support.