2021 WI App 40

COURT OF APPEALS OF WISCONSIN

PUBLISHED OPINION

Case No.: 2020AP919

Complete Title of Case: 

†Petition for Review Filed

IN RE THE MARRIAGE OF:

LISA M. ZIMMER,

 PETITIONER-APPELLANT,

STATE OF WISCONSIN,

 CO-APPELLANT,

 V.

MICHAEL P. ZIMMER,

 RESPONDENT-RESPONDENT.†

Opinion Filed: May 12, 2021

Submitted on Briefs: January 28, 2021

JUDGES: Neubauer, C.J., Reilly, P.J., and Davis, J.

Concurred:

Dissented:

Appellant

ATTORNEYS: On behalf of the plaintiff-appellant, the cause was submitted on the 

briefs of Emily E. Parks of Parks Law Offices, LLC, Fond du lac.

On behalf of the co-appellant, the cause was submitted on the brief of 

Clayton P. Kawski, assistant attorney general, and Joshua L. Kaul, 

attorney general. 
2

Respondent

ATTORNEYS: On behalf of the respondent-respondent, the cause was submitted on 

the brief of Daniel Kaminsky of Kaminsky Law, S.C., Fond du Lac. 
2021 WI App 40

COURT OF APPEALS

DECISION

DATED AND FILED

May 12, 2021

Sheila T. Reiff

Clerk of Court of Appeals

NOTICE

This opinion is subject to further editing. If 

published, the official version will appear in 

the bound volume of the Official Reports. 

A party may file with the Supreme Court a 

petition to review an adverse decision by the 

Court of Appeals. See WIS. STAT. § 808.10 and 

RULE 809.62. 

Appeal No. 2020AP919 Cir. Ct. No. 2014FA546

STATE OF WISCONSIN IN COURT OF APPEALS

IN RE THE MARRIAGE OF:

LISA M. ZIMMER,

 PETITIONER-APPELLANT,

STATE OF WISCONSIN,

 CO-APPELLANT,

 V.

MICHAEL P. ZIMMER,

 RESPONDENT-RESPONDENT.

APPEAL from an order of the circuit court for Fond du Lac County: 

PETER L. GRIMM, Judge. Reversed and cause remanded with directions. 

Before Neubauer, C.J., Reilly, P.J., and Davis, J. 
No. 2020AP919

2

¶1 DAVIS, J. Child support payments in a divorce are typically ordered 

as monthly lump sum payments derived under a formula prescribed by state law. 

That formula computes payments based on the payer’s income multiplied by a 

percentage, which varies depending on the number of minor children. See WIS.

ADMIN. CODE § DCF 150.03(1). Where multiple children are involved, as each 

child reaches the age of majority, the paying parent can seek modification to reduce 

ongoing payments to the remaining minor children, based on the reduced applicable 

percentage. All else being equal, the court would ordinarily order such modification 

upon the payer’s motion and reduce support payments accordingly. 

¶2 Less clear is what happens when the payer fails to promptly file such 

a motion and, instead, continues to pay or incur the original ongoing support amount 

for some time after one of the children ages out. The issue in such a case is whether 

an order on a belated modification motion can be given retroactive effect, so as to 

reduce or allow for a credit against arrears, or even a refund. Those are the facts 

here. Lisa Zimmer (Lisa) and the State1appeal from a circuit court order reducing

Michael Zimmer’s (Michael) child support arrears, entered as part of an action to 

modify child support. It is undisputed that Michael did not move to modify the 

support order concerning his three minor children until two years after the eldest, 

Heidi had reached the age of majority under WIS. STAT. § 767.511(4). Michael 

argued below that his support obligation should have “reduced automatically” when 

Heidi aged out and that the “overages” he paid should be credited towards arrears. 

The circuit court agreed and modified arrears accordingly. 

 

1

 The State appeals as a real party in interest under WIS. STAT. § 767.205(2)(a) (2017-18). 

All references to the Wisconsin Statutes are to the 2017-18 version. Except where expressly noted, 

we refer to the appellants collectively as “Lisa.”
No. 2020AP919

3

¶3 We conclude that our legislature has already decided whether a child 

support order can be applied retroactively, and has answered this question in the 

negative. Under WIS. STAT. § 767.59(1m), a payment modification order is 

prospective only. This means that a court cannot, on the basis of one child’s having 

reached the age of majority, refund or credit child support payments made prior to 

notice being given in an action to modify an ongoing support obligation. 

Consequently, we reverse.

BACKGROUND

¶4 Lisa and Michael married in 1993, had four children during the

marriage, and divorced in January 2016. The divorce judgment ordered Michael to 

pay “$3,266.62 per month commencing September 15, 2015” for the three children 

who were minors. Heidi, the eldest of the three, reached the age of majority in June

2017. By law, this event provided Michael grounds to reduce his support obligation, 

but he did not then move to do so. Two years later, in 

July 2019, Michael moved to modify the child support order, requesting that the 

“overages” he had paid since June 2017 be credited towards accumulated arrears.

¶5 A family court commissioner held a hearing on the motion and denied 

it, finding that the statutory child support scheme precluded it from modifying

arrears in this manner. Michael filed for de novo review in the circuit court. That

court reversed, relying on Wisconsin law holding that a court cannot order a parent 

to pay child support for an adult child. See Poehnelt v. Poehnelt, 94 Wis. 2d 640, 

655-66, 289 N.W.2d 296 (1980). The circuit court concluded that any support 

Michael paid for Heidi past her age of majority violated the law and was tantamount 

to an error in calculation. See WIS. STAT. § 767.59(1m) (the court may not revise 

child support amounts due, or arrearages accrued, prior to the date on which the 
No. 2020AP919

4

respondent is notified of the action, except to correct previous errors in calculation). 

The court calculated that Michael had paid $7722.05 in “overages” and credited this 

amount towards approximately $13,000 in arrears. This appeal followed.

DISCUSSION

¶6 Lisa argues that the circuit court erred when it credited towards arrears 

that portion of child support payments attributable to Heidi after she had reached 

the age of majority but before Michael provided notice to Lisa of his motion to 

modify child support. See WIS. STAT. § 767.59(1c)(a), (1m). According to Lisa, § 

767.59(1m) prohibits exactly this type of retroactive child support modification. 

Michael, in turn, points out that a court cannot order child support for an adult as a 

matter of law. See WIS. STAT. § 767.511(4); Poehnelt, 94 Wis. 2d at 655-56. By 

implication, Michael argues, the child support order became “a nullity” to the extent 

that it required payments for Heidi once she reached the age of majority. 

¶7 To resolve this issue, we turn to the relevant statute. WIS. STAT.

§ 767.59(1m), titled “Payment revisions prospective,” states:

In an action under [§ 767.59(1c)] to revise a judgment or 

order with respect to child support ... the court may not 

revise the amount of child support ... due, or an amount of 

arrearages in child support ... that has accrued, prior to the 

date that notice of the action is given to the respondent, 

except to correct previous errors in calculations.

Our legislature enacted the precursor to this statute in 1987 so as to “eliminate[] the 

long-standing power of the Wisconsin courts to modify, reduce, or forgive 

accumulated support arrearages.” Schulz v. Ystad, 155 Wis. 2d 574, 595-96, 456 

N.W.2d 312 (1990). In deference to this legislative prerogative, we have narrowly 

construed the statutory exception permitting modification for “previous errors in 

calculations,” holding that “[t]he legislature, by using the term calculation, restricted 
No. 2020AP919

5

the court’s authority to revise the amount of child support due or the amount of child 

support arrearages in mistakes of mathematical errors only.” See State v. Jeffrie 

C.B., 218 Wis. 2d 145, 149-50, 579 N.W.2d 69 (Ct. App. 1998). Thus, a court 

cannot retroactively alter a child support obligation to correct any non-mathematical 

mistake (for example, that the payer should have been subject to the lower rate 

applicable to a serial family payer, as was the case in Jeffrie C.B.). See id. at 147.

¶8 We conclude that the circuit court’s modification of Michael’s child 

support order was not akin to correcting a mathematical mistake. To the contrary, 

there was no error in the 2016 judgment: the ordered monthly amount properly 

reflected the fact that Michael then had three minor children. That judgment 

necessarily controlled in the absence of any motion to revise the child support 

obligation. See WIS. STAT. § 767.59(1c), (1f). Michael had the option of bringing 

such a motion in the months before Heidi reached the age of majority. His failure 

to do so does not constitute a “previous error[] in calculation[].” See § 767.59(1m). 

Thus, the circuit court improperly revised Michael’s child support obligation 

retroactively, contrary to § 767.59(1m).

2

¶9 In arguing otherwise, Michael relies on WIS. STAT. § 767.511(4), 

pursuant to which:

The court shall order either party or both to pay for the 

support of any child of the parties who is less than 18 years 

old, or any child of the parties who is less than 19 years old 

 

2

 We would reach the same result if Michael had no child support arrears (that is, if 

Michael were seeking a refund or were requesting that the amount he allegedly overpaid be credited 

towards future child support payments). WISCONSIN STAT. § 767.59(1m) only allows the court to 

modify child support prospectively, unless the court is correcting a mathematical error. State v. 

Jeffrie C.B., 218 Wis. 2d 145, 149-50, 579 N.W.2d 69 (Ct. App. 1998).

Notwithstanding WIS. STAT. § 767.59(1m), subsec. (1r) allows the circuit court to credit 

the payer for payments made under specified circumstances; for example, where the parents

resumed living together. Michael has not alleged that any condition in this subsection applies.
No. 2020AP919

6

if the child is pursuing an accredited course of instruction 

leading to the acquisition of a high school diploma or its 

equivalent.

Michael correctly points out that, accordingly, “courts have no authority to order 

support for a child beyond the age of majority defined by statute.” (Emphasis 

added.) It does not follow, however, that a valid child support order automatically 

becomes “a nullity” (as Michael argues) when one of the children covered by that 

order reaches the age of majority. Such occurrence might constitute “a substantial 

change in circumstances” justifying revision of the child support order, see WIS.

STAT. § 767.59(1f), but the court’s authority to do so is only triggered by “the 

petition, motion, or order to show cause of either of the parties” or various specified 

agencies, § 767.59(1c)(a). There is no statutory mechanism whereby the existing 

order is “nullified”; nor does the court, the state, or a child support agency have any 

related authority to unilaterally void the order or recalculate the support obligation.3 

¶10 Michael further points to case law supporting the general premise that 

a court cannot order child support for an adult child. To the extent these cases 

concern support to a child who is already an adult, they are inapplicable to the facts 

before us. See, e.g., Poehnelt, 94 Wis. 2d at 655 (“[I]n the absence of a known 

stipulation to the contrary, a court cannot order the payment of support for children 

 

3

 Michael speculates as to how his case would be treated if the child support order

delineated how much support were attributable to each child. It is not apparent why such wording 

would relieve Michael of his obligation to move to modify support, but in any event, these are not 

the facts before us, and we decline to address hypothetical scenarios. Michael further argues that 

it is unfair that, as a “payer for multiple children,” he is treated differently than a parent with only 

one child to support. This argument is curious to us, since Michael will be treated the same as a 

parent with only one child to support once his youngest child reaches the age of majority. We see 

no unfairness or due process concern in the state’s acting to terminate child support once the only 

(or youngest) child is above the age of majority, but not doing so when only one of multiple children 

ages out. In the former case, the child support obligation has ended. In the latter case, a “substantial 

change in circumstances” might warrant revisiting the support amount, but the obligation itself 

continues. See WIS. STAT. § 767.59(1f). 
No. 2020AP919

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beyond the age of majority. The provision for continued support for a child who 

has reached the age of majority in a divorce judgment, or any modification thereof, 

is extrajudicial and a nullity.” (citations omitted)); see also Roberta Jo W. v. Leroy 

W., 218 Wis. 2d 225, 230-36, 578 N.W.2d 185 (1998). To the extent these cases 

generally permit retroactive modification of a support award, they are overruled by 

the passage of WIS. STAT. § 767.59(1m), which, as explained above, eliminated the 

court’s broad ability to retroactively modify child support or arrears accrued. See, 

e.g., Poehnelt, 94 Wis. 2d at 655-57 (holding that the defendant was entitled to a 

$2800 credit for a child support “overpayment” resulting from a mistake in the 

divorce complaint as to the date of two children’s birthdays).

¶11 WISCONSIN STAT. § 767.59 provides the statutory mechanism for 

revising child support orders. That Michael waited two years to bring a motion 

under that section does not constitute an “error[] in calculation[]” authorizing a 

reduction in arrears. See § 767.59(1m). We remand to the circuit court with 
No. 2020AP919

2

instructions to reinstate the order of the family court commissioner denying 

Michael’s request to be credited for “overpayments.”4 

By the Court.—Order reversed and cause remanded with directions.

 

4

 We agree with the State that accepting Michael’s view of the law could create an 

administrative burden on child support agencies, which might become obligated to track when one 

of multiple children subject to a support order reached the age of majority and then notify the 

parents or petition the court to modify support. We further agree that a public policy problem could 

result if a parent were permitted to unilaterally reduce the child support obligation because one 

child had reached the age of majority, on the premise that any arrears incurred would thereby be 

forgiven. Certainly such a rule could adversely impact the welfare of the remaining minor children, 

for whom the support amount (once the credit or refund were issued) might be less than what they 

would otherwise receive or be entitled to. Moreover, by requiring a motion to modify support, our 

legislature enabled courts to revisit all relevant circumstances, such as changes in parental income, 

thereby ensuring that the remaining minor children receive the proper level of support. The 

requirement of a motion may also allow the court to revisit other issues that had been deferred 

pending the aging out of minor children. Here, for example, the divorce judgment determined that 

Michael could not then afford maintenance to Lisa, but the court held the matter open, it being “the 

court’s intention to allow the parties to reconsider the maintenance issue as ... Michael’s[] child 

support obligation decreases over time as each of the children age out.” We do not discuss Lisa’s 

arguments more fully, or address Michael’s responses to them, because the statutes and case law 

control the disposition of this appeal.