How to Complete and File the Wisconsin Child Support Modification Form FA-4170V

To change an existing Wisconsin child support order, you file Form FA-4170V, the Notice of Motion and Motion to Change, with the Clerk of Circuit Court in the county that issued your current order. The Wisconsin child support modification form FA-4170V is free to download from the Wisconsin Court System, and the filing fee is $30 when the motion involves only child support.¹² If both parents already agree and sign a stipulation, no filing fee applies. Uncontested cases can move through in a few weeks; contested cases can take several months.

Do You Have Grounds to File

Wisconsin will not revisit a support order without a “substantial change in circumstances.” That standard comes from Wisconsin Statutes Section 767.59(1f).³ You don’t have to prove the change is permanent, but you do need documented evidence.

The statute creates a rebuttable presumption of substantial change in several situations:

At least 33 months have passed since the current amount was set or last revised. This trigger does not apply if your order already expresses support as a percentage of income rather than a fixed dollar amount.
Either parent has begun receiving W-2 benefits or aid to families with dependent children since the last order.
The paying parent failed to provide the financial disclosure required by Section 767.54.
The original court set support at an amount different from the state percentage standard without explaining the deviation on the record.

Outside those automatic triggers, the statute recognizes other qualifying changes if you can prove them: a significant shift in the paying parent’s income or earning capacity, a change in the child’s needs, or any other factor the court finds relevant.³ Common examples are a permanent job loss, a child developing medical needs that increase expenses, or a change in the placement schedule that shifts how much time the child spends with each parent.

Filling Out FA-4170V

Download the form from the Wisconsin Court System’s circuit court forms page and pull out your most recent order before you start.⁴ You will need the county, case number, and the name of the judge or court commissioner who signed the current order.

Header and Parties

Enter the county and existing case number exactly as they appear on your most recent order. Then fill in full legal names, mailing addresses, and phone numbers for both parents. The address you list for the other parent is where your motion papers will be served, so get it right.

Child Support Section

Check the box asking the court to change support to an amount based on Wisconsin’s child support standards. Then indicate whether the new amount should include an adjustment for health insurance costs, and if so, whether that adjustment is upward or downward and by how much.⁴ State your current ordered amount and your proposed new amount. Being specific helps the court commissioner understand what you’re asking for before the hearing begins.

Reasons for the Change

Tie your explanation directly to one of the legal grounds above. Give dates and dollar figures. “I was laid off on March 15, 2026, and my monthly gross income dropped from $5,200 to $2,800 in unemployment benefits” gives the court something to work with. “Things have changed” does not.

Signature

Sign and date the form. Despite what some older guides suggest, FA-4170V does not require notarization. Print your name and include your address, email, phone number, and State Bar number if you are an attorney.⁴

Attach the Financial Disclosure Statement

Form FA-4139V, the Financial Disclosure Statement, is labeled voluntary, but skipping it is a mistake.⁵ The court needs a clear picture of your finances to recalculate support, and many county family court commissioner offices expect the disclosure as part of the filing package.

The form requires a full breakdown of monthly income, anticipated monthly expenses, and every asset you own individually or jointly with the other parent, including retirement accounts, pensions, real estate, and vehicles. For each vehicle, list the year, make, model, amount owed, and estimated current value.⁶ Attach a year-to-date income statement, your most recent W-2, and documentation for any public assistance you receive. Numbers on the form must match your supporting documents.

Filing With the Clerk and Paying the Fee

Take your completed FA-4170V, your FA-4139V with attachments, and copies for the court and the other parent to your county’s Clerk of Circuit Court. The statutory fee for a motion to change child support, family support, or maintenance is $30.² If your motion also asks the court to change legal custody or physical placement, the fee is $50. If both parents have signed a stipulation, there is no fee. If you can’t afford the fee, ask the court to waive it based on indigency.

Some counties want you to get a hearing date from the family court commissioner’s office before you file with the clerk. Oconto County, for example, has you visit the commissioner first, then take your papers to the clerk.⁷ Call your county clerk before you go so you don’t make two trips.

Serving the Other Parent

After filing, you have to make sure the other parent receives a copy of everything you filed. You cannot hand-deliver the papers yourself; service must be performed by a third party.⁸ The usual options are the sheriff’s department in the county where the other parent lives or a private process server. Sheriff service fees are set by statute at $65 per person served.² Private servers set their own rates.

Once service is done, file the proof of service with the clerk. Wisconsin uses an Admission of Service form when the other parent accepts the papers voluntarily and a Declaration of Service form when a server delivered them personally.⁸ Without filed proof of service, the hearing cannot go forward.

The Hearing

Depending on your county, the hearing is held before a family court commissioner or a judge. Both parents can present evidence and argue their positions. Bring originals of every document you referenced in your papers: pay stubs, tax returns, health insurance statements, proof of the child’s expenses, and any written communication showing a change in placement time. The court applies Wisconsin’s percentage-of-income guidelines to the current financial picture and decides whether to modify the order and, if so, by how much.⁹

If both parents agree on the new amount ahead of time, the commissioner can approve a stipulation in a single appearance. Contested cases run longer because the court may need to weigh conflicting financial claims, request more documentation, or schedule follow-up hearings. A modified order takes effect on the date the court signs it, not the date you filed.

Why You Should File Immediately

Federal law prohibits any state from retroactively reducing child support that has already come due. Under 42 U.S.C. Section 666(a)(9)(C), every installment becomes a fixed obligation on its due date and cannot be modified after the fact.¹⁰ Courts cannot forgive or reduce arrears that accumulated before you filed your motion, whatever the reason: illness, job loss, or incarceration. Every month you wait locks in the old obligation. If your circumstances have changed, file now.

Free Alternative Through the County Child Support Agency

You don’t have to file FA-4170V to get a review. Your local county child support agency will review an existing order at no cost. The agency has up to 180 days to complete a review and can either help the parents reach an agreement or refer the case to court if they disagree.¹¹ The agency will conduct a review when the order has not been reviewed in at least three years, when a parent receiving cash assistance asks for one, or when a court orders it.

The agency route is free but limited. It will not review your case if the paying parent voluntarily reduced their income, if the order comes from another state, or if all the children have reached adulthood. Filing FA-4170V directly gives you more control over the timeline and works in situations the agency won’t touch.

If a Parent Is on Active Military Duty

The Servicemembers Civil Relief Act lets an active-duty parent request a stay of the modification proceedings. Under 50 U.S.C. Section 3932, a servicemember who cannot appear because of military duties can apply for a stay of at least 90 days, with a letter explaining how current duty prevents appearance and a communication from the commanding officer confirming that leave is not authorized.¹² Additional stays can be requested if the conflict continues. If you are the servicemember, tell the court about your status early; the protection is not automatic.

A Note on Taxes

Modifying support does not change how it is taxed. Child support payments are not deductible by the paying parent and are not taxable income to the receiving parent.¹³ If tax dependency allocation is part of what you’re negotiating, raise it explicitly at the hearing rather than assuming the old arrangement carries over.

1
Wisconsin Court System. Notice of Motion and Motion to Change: Legal Custody, Physical Placement, Child Support, Maintenance or Arrears Payment
2
Wisconsin State Legislature. Wisconsin Code 814.61 – Fees in Circuit Court
3
Wisconsin State Legislature. Wisconsin Code 767.59 – Revision of Support and Maintenance Orders – Section 767.59(1f)
4
Wisconsin Court System. FA-4170V Notice of Motion and Motion to Change
5
Wisconsin Court System. Circuit Court Forms – FA-4139V
6
Wisconsin Court System. FA-4139V Financial Disclosure Statement
7
Oconto County, WI. Notice of Motion and Motion to Change – Section: Filing Instructions
8
Wisconsin Court System. Wisconsin Court System – Service
9
Wisconsin Department of Children and Families. Shared-Placement Worksheet to Estimate Support
10
Office of the Law Revision Counsel. 42 USC 666 – Requirement of Statutorily Prescribed Procedures
11
Wisconsin Department of Children and Families. Reviewing a Court Order for a Change
12
Office of the Law Revision Counsel. 50 USC Ch. 50 – Servicemembers Civil Relief
13
Internal Revenue Service. Alimony and Separate Maintenance