Wisconsin courts may consider all relevant financial information or information relevant to either parent's earning capacity when determining the amount of child support to be paid. However, Wisconsin has also adopted child support guidelines which presume that child support should be based on a percentage of that parent's gross income.

The child support guideline percentages that are applied are as follows:

These guidelines form a rebuttable presumption. Only under rare circumstances does a court deviate from these guidelines. In fact, in order for a Court to deviate from the percentage guidelines it must include in its order specific findings determining the amount of guideline support and its reasons why the guideline support is unfair to the child or either party. As part of the analysis, the Court must consider the following factors:

Child support may be reduced from guideline percentages if each parent shares physical placement. Shared physical placement is presumed when the child support payer has the child in their care no less than 30% of the time or 110 nights per year. If the payer cares for the child between 30-40% of the time, his/her child support obligation may be reduced from 100% of the guideline percentage to 67% of the guideline support figure. If the payer cares for the child between 40 and 60% of the time, his/her child support may be reduced from 67% of the guideline child support figure to $0.

On rare occasions a Court may award physical placement of some children to the mother and some children to the father. This is called split physical placement. In cases where the children are "split" between the parents, child support is determined by applying the child support guidelines to each parent's income based on the number of children in the other parent's care. The child support obligations are then offset by subtracting the smaller obligation from the larger obligation. (DWD40.04(3))

More and more often in today's society, parents are starting second and even third families. In such serial family situations child support may be reduced for the families that are started later in time. As a general rule, the first family in time receives guideline child support. The second family in time receives guideline child support after deducting the first child support obligation from the payer's income. A third family in time would receive child support based on guideline percentages only after the first and second child support obligations are deducted from the payer's gross income. This formula does not not consider additional children that the payer may be supporting in a current family.

Under Wisconsin Statutes, the Court also has the discretion to require a portion of any child support amount paid set aside in a separate fund or trust account for support, education or the welfare of the children. In practice, this is rarely put into effect unless the party paying child support has a significant income (usually in excess of $6000 gross per month or more).

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.