Yes and no. A Montana decree of dissolution has several parts, and the law treats them differently. Terms about children, meaning the parenting plan and child support, stay open to change because children's needs change. Maintenance (alimony) can be modified too unless the decree precludes it, on a demanding standard. The division of property and debts is meant to be final, with narrow exceptions. This article sorts the parts into those groups. It is part of our Montana Divorce Guide.
The Short Version
| Part of the decree | Can it change? | What it takes | MCA |
|---|---|---|---|
| Parenting plan | Yes | New or previously unknown facts show a change in the child's circumstances, and amendment is necessary to serve the child's best interest. | § 40-4-219(1) |
| Child support | Yes, going forward | Changed circumstances so substantial and continuing as to make the terms unconscionable, or written consent, or an application by the state child support agency. | § 40-4-208(1), (2)(b) |
| Maintenance | Yes, going forward, unless the decree precludes it | Same statutory standard as child support. A decree may expressly preclude or limit modification if the separation agreement provides for it. | §§ 40-4-208(2)(b), 40-4-201(6) |
| Property and debt division | Generally no | Only on written consent of the parties, or conditions that justify reopening a judgment under Montana law. | § 40-4-208(3) |
| The dissolution itself | No | The decree is final when entered, subject to appeal. | § 40-4-108(1) |
Modification is different from an appeal. An appeal argues that the court got it wrong on the record it had. A modification argues that things have changed since.
Parenting Plans
The court "may in its discretion amend a prior parenting plan if it finds, upon the basis of facts that have arisen since the prior plan or that were unknown to the court at the time of entry of the prior plan, that a change has occurred in the circumstances of the child and that the amendment is necessary to serve the best interest of the child" (MCA § 40-4-219(1)).
Three features of that sentence matter. The change must be in the child's circumstances. It must rest on new or previously unknown facts, not a second try at the original arguments. And the amendment must be necessaryfor the child's best interest. The statute adds that "preference must be given to carrying out the parenting plan" (MCA § 40-4-219(7)).
Parents who agree on a change can ask the court to approve it. Whether the parents agree is the first thing the statute tells the court to consider (MCA § 40-4-219(1)(a)(i)). See amending a parenting plan.
Child Support
When a decree contains support provisions, they may be modified only (MCA § 40-4-208(2)(b)):
- "upon a showing of changed circumstances so substantial and continuing as to make the terms unconscionable";
- upon written consent of the parties; or
- upon application by the Department of Public Health and Human Services when it is providing child support services.
A modified child support obligation is set under the Montana child support guidelines. A missing or violated medical support order justifies an immediate modification to provide for the child's medical care (MCA § 40-4-208(2)(c)).
The timing rule is strict. A decree may be modified "only as to installments accruing subsequent to actual notice to the parties of the motion for modification" (MCA § 40-4-208(1)). The court does not go back and forgive or increase what came due before that. Parents cannot make child support non-modifiable by agreement, because the statute that lets a decree preclude modification excepts terms concerning support of the children (MCA § 40-4-201(6)). See modifying child support.
Maintenance
Maintenance follows the same statute and the same standard: changed circumstances so substantial and continuing as to make the terms unconscionable, or written consent (MCA § 40-4-208(2)(b)). The word is "unconscionable," which asks for more than a showing that things are different or tighter than before.
Two special rules apply.
- Agreed limits. A decree "may expressly preclude or limit modification of terms set forth in the decree if provided for in the separation agreement" (MCA § 40-4-201(6)). If your decree has that language for maintenance, the court's power to change it is limited accordingly.
- Automatic termination. Unless otherwise agreed in writing or expressly provided in the decree, the obligation to pay future maintenance ends on the death of either party or the remarriage of the party receiving it (MCA § 40-4-208(4)).
There is also a rule about silence. Where a decree contains no provisions relating to maintenance or support, a modification under the statute may be made only within 2 years of the date of the decree, apart from the disclosure remedies discussed below (MCA § 40-4-208(2)(a)). If you waived maintenance, or the decree simply did not address it, do not assume the question stays open indefinitely. See modifying or ending maintenance.
Property and Debts: Final, With Narrow Exceptions
"The provisions as to property disposition may not be revoked or modified by a court except: (a) upon written consent of the parties; or (b) if the court finds the existence of conditions that justify the reopening of a judgment under the laws of this state" (MCA § 40-4-208(3)).
The second exception points to Montana's general rule on relief from judgments. Under Rule 60(b) of the Montana Rules of Civil Procedure, a court may relieve a party from a final judgment for reasons that include mistake, inadvertence, surprise, or excusable neglect; newly discovered evidence; fraud, misrepresentation, or misconduct by an opposing party; a void judgment; or any other reason that justifies relief. A motion must be made within a reasonable time, and for the first three grounds no more than a year after entry of the judgment (M. R. Civ. P. 60(c)(1)). The rule also preserves a court's power to set aside a judgment for fraud on the court (M. R. Civ. P. 60(d)(3)).
Dissolution cases have an added layer. A decree may be modified for failure to disclose assets and liabilities (MCA § 40-4-208(8)). Failure to disclose an asset or liability on the final declaration of disclosure is presumed to be grounds for awarding the undisclosed asset to the other party, or the undisclosed liability to the party who hid it. And the court may set aside all or part of a judgment if it discovers, within 5 years from entry of judgment, that a party committed perjury in the final declaration (MCA § 40-4-253(4), (5)). See reopening a divorce judgment.
What does not qualify: a change of heart, a bad bargain, or an asset that later rose or fell in value. Finality in the property division is deliberate. It lets both people plan. That is the reason to get the valuation and disclosure right before the decree.
Fixing Mistakes Versus Changing Terms
Not every problem needs a modification. A court may correct a clerical mistake, or a mistake arising from oversight or omission, whenever one is found in a judgment (M. R. Civ. P. 60(a)). A wrong account number or a misspelled name is that kind of error.
And sometimes the decree is fine but is not being followed. That calls for enforcement, not modification. Terms set out in the decree are enforceable by all remedies available for a judgment, including contempt (MCA § 40-4-201(5)). See enforcing a divorce decree.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the Montana Rules of Civil Procedure. It is not legal advice about your specific case.