You can change a final Montana parenting plan (what many people call modifying custody) in two ways: by agreement with the other parent, or by asking the court to amend it under MCA § 40-4-219. The court route has a specific test, and the statute discourages repeated trips back to court. This page explains both and is part of our Montana Divorce Guide.
The Test: New Facts, a Change, and Best Interest
Under MCA § 40-4-219(1), 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."
That sentence has three parts:
- New facts. They arose after the prior plan, or the court did not know them when it entered the plan.
- A change in the circumstances of the child. The statute speaks of the child's circumstances.
- Necessity. The amendment must be necessary to serve the child's best interest.
Even then, the word is "may." The decision is within the court's discretion, and the statute adds that "preference must be given to carrying out the parenting plan" (MCA § 40-4-219(7)). A "prior parenting plan" means a parenting determination contained in a judicial decree or order.
What the Court Considers
In deciding how a proposed change will affect the child, the court considers the potential impact on the best interest factors in MCA § 40-4-212 and whether (MCA § 40-4-219(1)(a)):
- the parents agree to the amendment;
- the child has been integrated into the family of the petitioner with consent of the parents;
- the child is 14 years of age or older and desires the amendment; or
- one parent has willfully and consistently refused to allow the child to have any contact with the other parent, or attempted to frustrate or deny contact with the child by the other parent.
The last item carries a consequence. The court "shall presume a parent is not acting in the child's best interest" if the parent does those acts (MCA § 40-4-219(3)). On the age 14 item, see does my child get to choose.
How a Motion to Amend Works
| Step | What the statute says | MCA |
|---|---|---|
| Try the plan's own process | A motion to amend is presumed vexatious if the parent has not made a good faith effort to comply with the plan or its dispute resolution provisions. | § 40-4-212(4)(b) |
| File a motion with a proposed amended plan | A proposed amended parenting plan must be filed and served with the motion, and with the response. | § 40-4-219(7) |
| Support it with an affidavit | Unless the parents agree, the moving parent submits an affidavit of supporting facts. The other parent may file opposing affidavits. | § 40-4-220(1) |
| Adequate cause | The court must deny the motion unless the affidavits establish adequate cause for a hearing, based on the child's best interests. | § 40-4-220(1) |
| Hearing | If adequate cause is shown, the court sets a show cause hearing on why the amendment should not be granted. | § 40-4-220(1) |
The adequate cause step is a screen. A motion that does not show, on paper, facts that would justify a hearing is denied without one. The court may also order the parents into a dispute resolution process such as counseling or mediation, except in cases of physical, sexual, or emotional abuse or threat of it, or when a parent has been convicted of one of the listed crimes (MCA § 40-4-219(9)).
Changing a Plan by Agreement
Parents who agree are in a different position. Agreement is the first consideration on the statutory list, and the affidavit requirement does not apply when the parties agree to an amended plan (MCA § 40-4-220(1)). The practical step is to write the amended plan, sign it, and submit it to the court so the order matches what you are doing.
A plan may also provide for periodic review at set points (MCA § 40-4-234(2)(f)), which gives parents a built-in occasion to adjust. A&M Law's Cooperative Family Law process can be used to work out an amended plan together.
Vexatious Motions and Fees
Montana law treats repeated parenting litigation as a harm to children. Three provisions work together:
- Attorney fees and costs "must be assessed against a party seeking frivolous or repeated amendment if the court finds that the amendment action is vexatious and constitutes harassment" (MCA § 40-4-219(5)).
- A motion to amend is rebuttably presumed vexatious if the parent has not made a good faith effort to comply with the plan or its dispute resolution provisions (MCA § 40-4-212(4)(b)).
- Adverse effects on the child from continuous and vexatious amendment actions are a best interest factor (MCA § 40-4-212(1)(m)).
None of this bars a parent with a real change in the child's circumstances from asking. It does mean a motion should rest on facts, and that following the existing plan while you ask matters.
Moves, Convictions, and Military Service
Three situations have their own rules inside § 40-4-219.
A parent's move. If one parent has changed or intends to change the child's residence in a way that significantly affects the child's contact with the other parent, the court also considers the feasibility of preserving the relationship with the nonrelocating parent, each parent's reasons, the relocating parent's willingness to promote the other relationship, and reasonable alternatives (MCA § 40-4-219(1)(b)). See relocating with a child.
Certain criminal convictions.If a parent, or another person living in that parent's household, has been convicted of one of the crimes listed in subsection (8)(b), which include deliberate homicide, sexual assault, incest, sexual abuse of children, endangering the welfare of children, partner or family member assault, and strangulation of a partner or family member, the other parent may file an objection to the current parenting order. The parent who receives notice has 21 days to respond. If there is no response, that parent's parenting rights are suspended until further order. If the parent responds and objects, a hearing must be held within 30 days of the response (MCA § 40-4-219(8)(a)).
Military service. A modification based in whole or in part on a parent's military service orders is temporary and reverts to the previous plan at the end of the service, unless the service member consents to something different. After the parent returns, the court may not consider the absence due to that service in determining the child's best interest (MCA § 40-4-219(10)). See military divorce in Montana.
If a change is needed because a child or parent is not safe, do not wait for the ordinary process. If you are in danger, call 911. The National Domestic Violence Hotline is 1-800-799-7233, and an emergency interim plan may be available under MCA § 40-4-220(2) where the child's present environment endangers the child's physical, mental, or emotional health.
This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific case.