Montana Child Support Calculator

Understanding Montana's Melson Formula

Montana calculates child support to meet your children's basic needs first before parents share any remaining income. Governed by MCA § 40-4-204, the state's Melson Formula ensures each parent can meet their own basic needs, covers the children's primary support, and then divides leftover parental income so your children can share in the family's standard of living.

How Shared Custody Impacts Support in MT

In Montana, a different formula is used when a child spends more than 110 overnights a year with each parent. Under the Administrative Rules of Montana (ARM) 37.62.140, this shared physical custody arrangement triggers a supplemental calculation that adjusts the final child support amount to reflect the increased costs of maintaining two separate households for the child.

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✓ Verified for 2026 Guidelines • Reviewed October 2026 by Harmoney

Montana Child Support Guidelines at a Glance

Guideline Model Melson Formula
Governing Legal Authority MCA § 40-4-204; ARM 37.62.101 et seq.
Shared Custody Threshold 110 Overnights (30% time)
Age Support Ends Age 18 (or 19 if still in High School)
Modification Standard 15% Change in Support Amount

Montana Child Support FAQs


At what age does child support end in MT?

Child support in Montana ends when a child turns 18, but it can extend to age 19 if the child is still enrolled full-time in high school. This obligation is established under Montana Code Annotated (MCA) § 40-4-208(5) and terminates automatically unless a court order specifies otherwise.

How is child support calculated if one parent is unemployed in MT?

If a parent is unemployed or underemployed without a good reason, Montana courts will impute income to them based on their earning capacity. The court determines this potential income by considering the parent's work history, qualifications, and local job opportunities, as outlined in the Administrative Rules of Montana (ARM) 37.62.106.

How do I modify a child support order in MT?

You can modify a child support order in Montana if there is a substantial and continuing change in circumstances that results in a 15% or greater change in the calculated support amount. This threshold is defined in Montana Code Annotated (MCA) § 40-4-208, and you must file a formal motion with the court to request the modification.

Does MT child support cover college expenses?

No, Montana law does not require a parent to pay for college expenses as part of child support after the child reaches the age of majority. Parents may, however, voluntarily agree to contribute to college costs and make that agreement part of a legally binding court order.

How does MT handle health insurance and childcare costs?

The cost of health insurance premiums and necessary work-related childcare are added to the basic child support obligation and are prorated between the parents based on their respective shares of the combined parental income. These specific provisions are detailed in the Administrative Rules of Montana (ARM) 37.62.110 and 37.62.112.