A Montana divorce judgment can be reopened, but only on specific legal grounds and usually within firm time limits. The property division in particular may not be revoked or modified unless both parties consent in writing or the court finds conditions that justify reopening a judgment under Montana law (MCA § 40-4-208(3)). Those conditions come from two places: Rule 60 of the Montana Rules of Civil Procedure, and the financial disclosure statutes. This page explains both, as part of our Montana Divorce Guide.
Why Decrees Are Hard to Reopen
A decree of dissolution is final when entered, subject to the right of appeal (MCA § 40-4-108(1)). Finality is the point: both people need to be able to rely on the division of property and move on. That is why the statute treats the property provisions differently from support. Maintenance and child support can be modified going forward on a showing of changed circumstances. Property cannot.
Reopening is also different from an appeal. An appeal asks the Supreme Court to review the district court's decision for error, and it must be started within 30 days. See appealing a divorce decree. A motion to reopen asks the district court itself to relieve a party from its own judgment.
The First 28 Days: Rule 59 and Rule 52
The earliest tools are the post-trial motions. A motion for a new trial, and a motion to alter or amend a judgment, must each be filed no later than 28 days after entry of judgment (M. R. Civ. P. 59(b), (e)). After a nonjury trial, the court may open the judgment, take additional testimony, amend its findings and conclusions or make new ones, and direct the entry of a new judgment (M. R. Civ. P. 59(a)(2)). A motion to amend the findings has the same 28-day limit (M. R. Civ. P. 52(b)).
These motions have a built-in clock for the court as well. If the court does not rule within 60 days of filing, the motion is deemed denied, unless the court extends its own time, and in no event later than 120 days (M. R. Civ. P. 59(f)).
Rule 60(b): Six Grounds for Relief
After that window, the main route is Rule 60(b). On motion and just terms, the court may relieve a party from a final judgment for the following reasons:
| Rule | Ground | Time limit (Rule 60(c)(1)) |
|---|---|---|
| 60(b)(1) | Mistake, inadvertence, surprise, or excusable neglect | Reasonable time, and no more than a year |
| 60(b)(2) | Newly discovered evidence that, with reasonable diligence, could not have been discovered in time to move for a new trial | Reasonable time, and no more than a year |
| 60(b)(3) | Fraud, misrepresentation, or misconduct by an opposing party | Reasonable time, and no more than a year |
| 60(b)(4) | The judgment is void | Reasonable time |
| 60(b)(5) | The judgment has been satisfied, released, or discharged; it rests on an earlier judgment that was reversed or vacated; or applying it prospectively is no longer equitable | Reasonable time |
| 60(b)(6) | Any other reason that justifies relief | Reasonable time |
Every Rule 60(b) motion must be made within a reasonable time. For the first three grounds there is also an outer limit of no more than a year after the entry of the judgment or order (M. R. Civ. P. 60(c)(1)). A Rule 60(b) motion is also deemed denied if the court does not rule within the time allowed by Rule 59(f).
Courts have interpreted each of these grounds in many decisions, and whether a particular set of facts fits one of them is a question for a lawyer who can read your file. In general terms, the rule is aimed at a judgment that was obtained unfairly or by mistake, not at a judgment that turned out to be a poor bargain.
Other Powers Rule 60 Preserves
Rule 60 also covers smaller and larger problems:
- Clerical mistakes. The court may correct a clerical mistake or a mistake arising from oversight or omission whenever one is found, on motion or on its own (M. R. Civ. P. 60(a)). A wrong account number or a misspelled name is fixed this way, not by reopening the case.
- Independent action. The rule does not limit a court's power to entertain an independent action to relieve a party from a judgment (M. R. Civ. P. 60(d)(1)).
- No personal notice. Nor does it limit the power to grant relief to a defendant who was not personally notified of the action (M. R. Civ. P. 60(d)(2)).
- Fraud on the court. The court keeps the power to set aside a judgment for fraud on the court (M. R. Civ. P. 60(d)(3)).
The Disclosure Statutes: Undisclosed Assets and Perjury
Montana's financial disclosure statutes carry their own consequences, separate from Rule 60. Each spouse signs the preliminary and final declarations of disclosure under penalty of perjury.
- If the court discovers that a party committed perjury in the preliminary declaration, it may set aside the judgment or part of it (MCA § 40-4-252(6)).
- If the court discovers, within 5 years from the date of entry of judgment, that a party committed perjury in the final declaration, it may set aside the judgment or part of it (MCA § 40-4-253(5)).
- Failure to disclose an asset or liability on the final declaration is presumed to be grounds for the court to award the undisclosed asset to the other party, or the undisclosed liability to the party who did not disclose it (MCA § 40-4-253(4)).
The modification statute ties these together. It says a decree may be modified, as provided in MCA §§ 40-4-251 through 40-4-258, for failure to disclose assets and liabilities (MCA § 40-4-208(8)), and the same exception appears in the statute on separation agreements (MCA § 40-4-201(7)).
Summary Dissolutions
A summary dissolution has its own rule. The final judgment does not bar either party from an action to set it aside for fraud, duress, accident, mistake, or other grounds recognized at law or in equity, or from a motion under the Rules of Civil Procedure. And the court shall set aside the judgment on all matters except the status of the marriage on proof that the parties did not meet the requirements for summary dissolution on the date the petition was filed (MCA § 40-4-135). See summary dissolution in Montana.
When You Do Not Need to Reopen Anything
Some problems that feel like a reason to reopen are really requests to modify or enforce:
- Circumstances changed. Maintenance or child support in a decree may be modified on a showing of changed circumstances so substantial and continuing as to make the terms unconscionable, or on written consent (MCA § 40-4-208(2)(b)). See modifying or ending maintenance and modifying child support.
- The parenting plan no longer fits. See amending a parenting plan.
- Your former spouse is not complying. That calls for enforcement. See enforcing a divorce decree.
- You both agree to a change. Property provisions may be modified on the written consent of the parties (MCA § 40-4-208(3)(a)).
If you believe a real ground exists, gather the decree, both sets of disclosure declarations, and whatever shows what you learned and when you learned it. Timing is part of every one of these remedies.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the current Montana Rules of Civil Procedure. It is not legal advice about your specific case.