Montana Child Support Calculator

Montana calculates child support using the Modified Melson Formula under MCA § 40-4-204, one of only three states using this model. The formula first deducts a personal allowance (1.3× the federal poverty guideline) from each parent's income, then determines a primary support obligation based on combined remaining income and number of children. An additional percentage applies to income above the primary obligation to maintain the child's standard of living.

Montana child support guidelines consider each parent's gross income from all sources, including wages, self-employment, investments, and benefits. Under ARM 37.62.105, courts impute at least full-time minimum wage (40 hours per week) to any parent capable of working. Parents who attempt to hide income or avoid employment may have earning capacity assigned based on education level and work history.

Montana's guidelines adjust child support when a child spends more than 110 days per year with each parent, reflecting the shared parenting time arrangement. In split parenting situations — where at least one child lives primarily with each parent — the formula applies separate calculations for each household. The parent with higher income or less parenting time typically pays more under the Modified Melson Formula.

Either parent may request a child support modification in Montana. Under MCA § 40-4-208, a judge may modify an existing order if both parents agree in writing, or if one parent demonstrates a continuing change of circumstances so significant that the current order is 'unconscionable.' The CSSD also conducts periodic reviews every four years under MCA § 40-5-209 to ensure guidelines meet Montana families' needs.

Beyond the base support amount, Montana's guidelines include adjustments for childcare costs required because of a parent's employment, health insurance premiums for the child, and unreimbursed healthcare expenses. Under MCA § 40-4-204, courts also consider the child's educational and emotional needs, each parent's financial resources, and the standard of living the child would have enjoyed if the family remained intact.

Montana does not set a statutory maximum child support amount — the Modified Melson Formula scales with parental income. The formula does establish a floor: each parent's personal allowance (1.3× the federal poverty guideline for one person) is protected before calculating support obligations. Courts impute at least full-time minimum wage income to parents capable of working, establishing an effective minimum calculation baseline.

Montana child support typically ends when the child turns 18 or graduates from high school, whichever occurs later, but always terminates by age 19. Support ends earlier if a child marries, joins the military, or becomes legally emancipated before age 18. Courts may extend support beyond age 18 for children with severe disabilities that began before adulthood, as determined on a case-by-case basis.

Montana's CSSD enforces child support orders through multiple mechanisms: automatic income withholding from paychecks, interception of federal and state tax refunds, seizure of bank accounts, liens on property, credit bureau reporting, and suspension of driver's and professional licenses. Courts may also hold non-paying parents in contempt, which can result in jail time. Montana's automatic payroll deduction system creates official records and prevents missed payments.