In the state of California there is no statute of limitations; child support is enforceable until paid in full. If you are wanting to get the back child support dismissed that cannot be done, the court will not dismiss the back child support. Depending on how long ago the child support is owed for the custodial parent may be able to have the child support dropped as long as he/she has never recieved any state benefits, the custodial parent can contact the child support services and tell them that the child support has been paid, but you would need to contact the parent to see if he/she would be willing to do this.

If the child is not on a TANF (temporary aid for needy families) grant AKA welfare then child support sends a letter to the person who is owed asking if they would still like child support services. Usually if the child has not been on a welfare grant by the time they are 18 the state closes the case. At least that has been my experience here in California. No child support was ever collected for my children and when they turned 18 their cases were closed.

In responds to trneza at the age of 18 ir is true child support ends if the child is still not attending high school. When the child support does end and the case is closed that is for the current child support, this has no bearing on any back child support erarages, if owed, theses erarages can be enforced at anytime the custodial parent choose's to prusue their child support order. It is also known to happen if the noncustodial parent has a child sopport order and the custodial was on welfare that the welfare can and usally will except a payoff on back child support if when the agreement is made the noncustodial pays the full amount agreed on at the time it is made.