How to modify child support or maintenance in Montana

Sources last checked: 4 November 2026. Information only, not legal advice. The Cusp is not a law firm.

Montana divorce kit How child support is calculated Alimony in Montana Legal aid in Montana After your divorce

The short version

Montana’s statutes call alimony “maintenance”. A court can change maintenance or child support under Montana Code Annotated (MCA) 40-4-208. The key timing rule is that a decree can be changed only as to “installments accruing subsequent to actual notice to the parties” of the motion, so a change does not reach back before the other side has notice. If the decree already deals with maintenance or support, the statute allows a change on a showing of “changed circumstances so substantial and continuing as to make the terms unconscionable”, on written consent of the parties, or on application by the state health department when it is providing child support services. We did not find a Montana court form for changing support or maintenance, and child support also has a separate route through the state’s Child Support Services Division, described below.

What a request can ask for

The test: section 40-4-208(2)(b), quoted above. The statute does not define “unconscionable”. Subsection (2)(a) adds that if the decree has no maintenance or support provisions, a change under subsection (1) may be made only within 2 years of the date of the decree.
A waiting period: under the same subsection, a modification “may not be made within 12 months after the establishment of the order” or the most recent modification. The statute makes exceptions for sections 40-4-251 to 40-4-258, which cover failure to disclose assets and liabilities.
Child support amount: when a court “issues or modifies an order concerning child support” it applies the state guidelines. The guideline amount is “presumed to be an adequate and reasonable support award” unless the court finds by clear and convincing evidence that it is unjust or inappropriate, and a court that departs from it must state its reasons (section 40-4-204(3)).
Medical support: section 40-4-208(2)(c) says a missing medical support order, or a violation of one, “justifies an immediate modification of child support” to cover the child’s medical costs or health coverage.
When maintenance ends: unless the parties agreed otherwise in writing or the decree says otherwise, maintenance ends on the death of either party or the remarriage of the person receiving it (section 40-4-208(4)).
When child support ends: by the child’s emancipation or graduation from high school, whichever is later, but “in no event later than the child’s 19th birthday”, unless extended or waived in writing or by the decree. Subsection (6) keeps support going past that age for a child with a disability who is financially dependent on the custodial parent. Support does not end when a paying parent dies; the court may modify, revoke or commute it.
Property: section 40-4-208(3) says provisions on property disposition “may not be revoked or modified by a court except” on written consent or where the grounds for reopening a judgment exist.
Where an agreement controls: section 40-4-201(6) says the decree “may expressly preclude or limit modification of terms set forth” from a separation agreement, other than terms about the support, parenting or parental contact with children. Otherwise, agreement terms in the decree are automatically modified when the decree is modified. Check your decree for that language.

Two routes for child support

Through the court: the Montana Courts forms pages we read list no form for modifying support or maintenance. The Motions page links a “District Court Motion Packet”. The PDF is headed Eleventh Judicial District Court and marked Revised November 2013, and it is a general motion packet, not one for support. It says you must fill out three forms: a Motion, an Affidavit, and a proposed Order. It also says you must give the other side a copy of what you file “by either 1st class mail or hand delivery” and that “you always must follow the Local Rules for the Court” where your case is pending. We did not confirm that a motion on this packet is the correct filing for a support modification.
Through the Child Support Services Division (CSSD): the CSSD page says you may ask it to review a support order “at least 36 months since the date the order was entered” or last reviewed. Sooner than that, you must show “a significant change of circumstances”. Its examples include a change in physical custody, in the child’s daycare or medical expenses, in the number of children, or income of a parent that has “changed by at least 30%”. Both parents may consent. If either does not agree, a hearing may be requested and an administrative law judge decides the amount. CSSD says the process “usually takes no more than 180 days”, and that a modification needing District Court involvement takes additional steps.
Starting a CSSD review: a parent submits a Request for Review packet. The page says it is obtained by contacting the investigator assigned to your case. CSSD checks the packet, confirms financial information, calculates the new obligation with the Montana Child Support Guidelines, and serves a notice. The page warns that the notice has set time limits for requesting a hearing and that if neither parent contacts CSSD “the notice will be finalized by default”.

Forms and calculation tools

The Montana Courts Child Support forms page lists a Montana Child Support Guidelines Packet from CSSD, which includes the guidelines and a worksheet. It describes its calculation tools as meant for people in a District Court proceeding such as a “Modification of Child Support Order”, and warns they “may not be the best resource for every case”. It also says that people who receive public assistance are automatically referred to CSSD.

Fee waiver: the Montana Courts site lists a “Request for Waiving Court Fees” among its divorce forms, and its forms index mentions a Statement of Inability to Pay Court Costs and Fees. We did not open either form, so we give no revision date or instructions.
Court Help Program: the Supreme Court describes it as “a free service provided by the Montana Supreme Court” for civil legal problems. Staff say they cannot give legal advice or represent you in court.

Before you file

Court staff cannot give legal advice. See legal aid in Montana for free or low-cost help, or the Montana divorce kit for the wider process.
Timing matters: a change reaches only payments after the other side has actual notice of the motion, so act as soon as your circumstances change, and keep proof of when the other side received it.
Gather your current decree or support order and your income records first, since the test turns on what has changed since the order.
Check the decree and any settlement agreement for language that limits modification.
Child support amounts follow the state guidelines. See how child support is calculated in Montana and alimony in Montana. For other changes after a divorce, see After your divorce.

What we could not confirm

A court form to modify support or maintenance. We found none on the Child Support, Divorce and Motions forms pages of the Montana Courts site. We did not read the other forms pages, such as Child Custody or Parenting Plans, so a form could exist elsewhere.
What “unconscionable” means in practice. The statute does not define it, and we read no court opinions.
Which filing starts a court modification. The general motion packet we read comes from one judicial district and dates from 2013. We did not read the Montana Rules of Civil Procedure, the Uniform District Court Rules, or any county’s local rules.
Whether the CSSD examples apply in court. The 36-month and 30 percent figures come from the CSSD page about its own review. The court test we read is the statute’s.
Guideline amounts. We did not read the Montana Child Support Guidelines or the administrative rules behind them, so this page gives no support figures.
Filing fees and fee waiver steps. We found no fee amount on the pages we read and give none. We did not open the fee waiver form.
Rules for maintenance in particular. We read section 40-4-203, which governs the first award, and it says nothing on modification. We read no rule on how long maintenance may last, and nothing on cohabitation.
Sections 40-4-251 to 40-4-258. Section 40-4-208 refers to them for failure to disclose assets and liabilities. We did not read them.
CSSD forms. We did not read the CSSD forms page or the Request for Review packet.

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