Montana Child Support Calculator

Estimate Montana child support for 2026 using the Melson Formula (Montana variant) guideline model under Mont. Admin. R. 37.62.101 et seq.. Enter both parents' incomes and the parenting-time split to see what you may owe or receive.

Montana uses the Melson Formula. The court first sets aside a self-support reserve for each parent's basic needs and a primary support amount for the children, then divides any remaining income with a standard-of-living adjustment so children share in the parents' income above subsistence.

Montana accounts for parenting time through a shared-care formula built into the Melson calculation. When both parents have meaningful overnight time, the worksheet adjusts each parent's share to reflect the costs each one carries while the children are in their home. More balanced parenting time can lower the amount the higher-earning parent pays, but the result still depends on income, the self-support reserve, and the children's primary needs. The on-page calculator gives a rough estimate only, and the official worksheet controls the final figure.

In Montana, the cost of the child's health insurance premium is treated as an add-on under Mont. Admin. R. 37.62.101 et seq. After the Melson Formula funds each parent's self-support reserve and the children's primary support, the premium is added and split between the parents pro rata based on their incomes. The parent who actually pays the premium usually receives credit toward their support obligation. The on-page calculator is an estimate, so confirm the exact split on the official worksheet or with a licensed attorney.

Work-related child care and daycare costs are handled as an add-on in Montana's Melson calculation. Once self-support and the children's primary needs are funded, reasonable child care expenses tied to a parent's employment are added to the support obligation and divided between the parents pro rata according to their incomes. Keep receipts and provider statements, because these numbers feed directly into the worksheet. The calculator on this page only estimates the result, and the official Montana worksheet remains the controlling document.

A Montana court may deviate from the guideline number when applying the Melson Formula would be unjust or inappropriate in a particular case. The guideline amount is presumed correct, so the parent asking the judge to depart from it carries the burden of showing why a different figure better serves the children. The judge must put written findings in the record explaining the reason for any deviation. Because deviations are fact-specific, treat the calculator here as an estimate and rely on the official worksheet or a licensed attorney for your actual case.

Frequently asked questions

How is child support calculated in Montana?

Montana uses the Melson Formula, set out in Mont. Admin. R. 37.62.101 et seq. The court first carves out a self-support reserve so each parent can meet basic subsistence needs, then funds the children's primary support. Any income left over is divided through a Standard of Living Adjustment so the children share in income above subsistence. Income counts from all sources, then is reduced by federal and state taxes, FICA, mandatory retirement, mandatory union dues, and a personal allowance. The Montana Child Support Services Division administers the program. The calculator on this page is an estimate only, and the official worksheet or a licensed attorney controls.

Is there an official Montana child support worksheet I have to use?

Yes. Montana's child support amount is determined by the official guideline worksheet that applies the Melson Formula under Mont. Admin. R. 37.62.101 et seq. That worksheet, not any online tool, is the controlling form a judge relies on. It walks through each parent's income, the allowed deductions, the self-support reserve, the children's primary support, the Standard of Living Adjustment, and add-ons like health insurance and child care. The Montana Child Support Services Division at dphhs.mt.gov/CSED can point you to the current forms. Use the estimate on this page to prepare, then complete the official worksheet or consult a licensed attorney before filing.

What income does Montana count when figuring child support?

Montana starts with income from all sources for each parent, then reduces it by allowable deductions before running the Melson Formula. Those deductions include federal and state taxes, FICA, mandatory retirement contributions, mandatory union dues, and a personal allowance that represents each parent's basic subsistence needs. Because the formula protects a self-support reserve first, low earners keep enough to live on before the children's share is calculated. Wages, self-employment earnings, and other regular income generally count. The calculator here estimates using these net-with-deductions principles, but the official Montana worksheet and a licensed attorney determine exactly how your income is treated.

How does shared or 50/50 parenting time change support in Montana?

Montana builds parenting time into the Melson calculation through a shared-care formula. When both parents have substantial overnight time with the children, the worksheet adjusts each parent's obligation to reflect the day-to-day costs each one covers in their own home. A more even split can reduce what the higher earner pays, but it does not automatically zero out support, because income differences and the children's primary needs still drive the result. Document your actual overnight schedule carefully. The on-page calculator only estimates this adjustment, so verify your figure on the official worksheet or with a licensed Montana attorney.

Can a parent be ordered to pay if they are unemployed or underemployed in Montana?

Yes. Montana's Melson Formula relies on each parent's income, and a court can address a parent who is voluntarily unemployed or working below their ability. In those situations the worksheet can reflect an earning capacity rather than zero, so a parent cannot avoid support simply by not working. The self-support reserve still protects basic subsistence needs, so the formula does not leave a low or no-income parent destitute. Because imputing income is fact-specific, the judge weighs work history and opportunities. Treat the calculator here as an estimate and rely on the official worksheet or a licensed attorney for your case.

When does child support end in Montana?

Montana child support generally continues until the child turns 18, or until the child graduates from high school, whichever comes later, but not past age 19. So a child who is still finishing high school at 18 may have support continue a bit longer, while a child who graduates earlier typically ends at 18. Continuing support may be available for a disabled adult child who cannot support themselves. Support does not stop automatically in every case, so confirm the terms of your order. The calculator here is an estimate, and the official worksheet or a licensed attorney controls the actual end date.

How do I modify a Montana child support order, and how is it enforced?

You can modify a Montana order by filing a motion in district court or requesting a review through the Child Support Services Division. A 25 percent variance between your current order and a fresh guideline calculation creates a presumption of a substantial change in circumstances, which supports modifying the amount. On the enforcement side, Montana CSSD uses immediate income withholding, tax intercept, license suspension, credit reporting, lien filings, and contempt referrals to collect support and arrears. Run the numbers on this page to see whether the 25 percent threshold may apply, then confirm with the official worksheet or a licensed attorney.