What Counts as a Substantial and Continuing Change for Child Support in Montana

By the FigureMyTax Editorial Team · How we calculate

To modify Montana child support you must show changed circumstances so substantial and continuing as to make the terms unconscionable, and not within 12 months of the order. A change can start only from actual notice of the motion.

What is a substantial and continuing change for child support in Montana?

Where the decree already has support provisions, it may be modified only 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 department when it provides IV-D services; the obligation is then set under the guidelines (MCA 40-4-208(2)(b)). Unconscionable is a high bar: a modest change that leaves the terms workable is unlikely to qualify.

Is there a percentage rule in Montana?

Not in the statutes we read. The department’s review ground refers to a substantial change “as defined by administrative rules” (40-5-272(4)(a)), which we did not verify here. The Montana child support modification calculator therefore shows the gap and the 12-month wait and does not give a pass or fail on a percentage.

For example, an $800 order against a $1,000 guideline amount is 25% lower than the guideline; whether that is unconscionable is for the court.

Does the department’s review use a different test?

Yes. The department can review an order on a rule-defined substantial change, health care needs, a 36-month lapse or a change in custody (MCA 40-5-272(4)), so a review may be open to you when a court motion would face the unconscionable standard.

What do the courts say about unconscionable?

The statute uses the word and does not define it; expect the court to ask whether the terms have become grossly unfair given a lasting change. Short-term changes and ordinary raises or pay cuts are usually not enough. Gather evidence that the change will continue.

What is the 12-month wait?

A modification under this subsection may not be made within 12 months after the establishment of the order or the most recent modification (40-4-208(2)(b)). If your order is newer than that, wait, but give thought to the medical support exception.

Is there a faster route for medical support?

Yes. The nonexistence of a medical support order, or a violation of one, justifies an immediate modification to provide for the child’s medical costs, provide or maintain health coverage, or remove a medical support credit that was used in setting support (40-4-208(2)(c)).

What can the department review?

On application of the department, the obligor or the obligee, the department can review an order to see whether it should be modified under the guidelines. Sufficient grounds include a substantial change in circumstances as defined by rule, the child’s health care needs, a lapse of 36 months since the order, an administrative hearing or a denial order, and a change in custody (40-5-272(1), (4)).

From what date can the order change?

A decree may be modified only as to installments accruing after actual notice to the parties of the motion (40-4-208(1)). Every month before notice is lost:

Federal law also bars retroactive modification of support already due (42 U.S.C. 666(a)(9)).

What happens next?

Read how to modify child support in Montana for the filing steps, and check what stays owed with the Montana arrears calculator.

Frequently asked questions

Official sources

• MCA 40-4-208: modification and termination of support
• MCA 40-4-204: child support orders; guidelines; withholding
• MCA 40-5-272: application for review of child support orders
• MCA 40-5-278: limited review of support order
• 42 U.S.C. 666(a)(9): no retroactive modification of support already due

This is general information, not legal advice. It is based on the cited Montana statutes, rules and court opinions, and every case turns on its own facts. Confirm how the law applies to your situation with a licensed Montana attorney.