In Wisconsin, an award of child support is subject to modification if future circumstances warrant revision. Johnson v. Johnson, 78 Wis.2d 137, 143-44, 254 N.W.2d 198 (1977).

Wisconsin Stat. § 767.32 governs the analysis employed when deciding a motion to modify child support. Specifically, the statute states that "a revision, of a judgment or order with respect to an amount of child or family support may be made only upon a finding of a substantial change of circumstances." Wis. Stat. § 767.32(1)(a). This requires a comparison between the parties' past and present financial circumstances. A change in payer's income, may constitute a substantial change of circumstances sufficient to justify a revision of the judgment or order. Wis. Stat. § 767.32(1)(c)(1).

The burden is upon the party seeking modification to show that the circumstances upon which the initial order was based have materially changed. Thies v. MacDonald, 51 Wis.2d 296, 301, 187 N.W.2d 186 (1971). Having found that a substantial change in circumstances has occurred, it is within the trial court's discretion to modify or refuse to modify the child support award. Long v. Wasielewski, 147 Wis.2d 57, 60, 432 N.W.2d 615 (Ct.App.1988).

Wisconsin Statutes sets forth percentage standards based on a payer's gross income that form a rebuttable presumption of what is a fair amount of child support to pay. The Court for many years set support based on a percentage of income when the payer's income fluctuated recently, Wisconsin statutes have been modified requiring all child support obligations to be expressed as a fixed monthly figure.

A Court may deviated from the expressed percentages if it finds that use of the percentage standards is unfair to the child or either party.

It is also important to recognize that issues of child support and interference with visitation or physical placement are not related. In short, one parent may not refuse the other parent access to the children because child support is not paid and vice versa.

An obligation to pay child support terminates at the age of 18 or at the age of 19 if the child is still attending classes in pursuit of a high school diploma or a GED. In the event a delinquency in child support exists, the party that is required to pay child support will also be required to pay interest on the unpaid amount at a rate of 1% per month. This is mandatory interest under the statute and a court has no discretion to terminate the interest payment.

Although a Court cannot extend child support beyond the age of nineteen, parents may agree to an extension of child support or payment of college tuition as part of the divorce, legal separation or annulment proceeding. Such agreements become enforceable between the parties and non-compliance may be enforced through contempt proceedings.