Non-payment of child support is a serious matter. Child support payments can only be discharged if they are paid in full, if there is a mistake made in the calculation of child support arrears, the order contains a legal mistake, or the child support was satisfied in another way.
If a parent cannot prove the support was paid when due, the court will order that parent to repay the child support, with interest. Sometimes there is a mistake in the amount alleged as arrearages.
Child support can discharged by satisfying the obligation in other ways. For instance, if the parent had custody during a period when support was ordered, the obligation will be satisfied for that time period. Sometimes expenses paid for the children can be used to offset arrearages. Normally, monies given directly to the child are not support, but, rather, they are a gift.
Finally, support can be discharged if the parties agree reach some sort of agreement. However, no monies can be owed for welfare arrears, and the agreement must be placed in a court order and signed by the court.