How Child Support Is Calculated in Montana

Montana calculates child support by taking each parent's income, subtracting allowed deductions and a personal allowance, and dividing the child's needs between the parents in proportion to what remains. The method is set out in the Montana Child Support Guidelines, ARM 37.62.101 through 37.62.148, which a court must apply in every case (MCA § 40-4-204(3)(a)). This page is part of our Montana Divorce Guide and follows the worksheet in order. It is an outline of the method, not a calculator.

The Calculation at a Glance

Income and Deductions

The starting point is each parent's annual income. Income for child support "includes actual income, imputed income ... or any combination thereof which fairly reflects a parent's resources available for child support" (ARM 37.62.105(1)). Our page on what counts as income covers the list and the exclusions.

From that figure the guidelines subtract allowable deductions. These include actual income tax liability, Social Security and Medicare actually paid, court-ordered maintenance, support paid for other children under an existing order, mandatory retirement contributions, and unreimbursed expenses required as a condition of employment (ARM 37.62.110(1)). Voluntary payroll deductions such as savings and credit union payments are not deductible (ARM 37.62.111(1)(a)). The rule notes that these deductions differ from deductions for tax purposes (ARM 37.62.110(2)).

The Personal Allowance

Each parent then subtracts a personal allowance, "an amount which reflects 1.3 multiplied by the federal poverty guideline for a one-person household" (ARM 37.62.114(1)). The rule describes it as a contribution toward, but not intended to meet, a parent's subsistence needs. In the Child Support Services Division tables effective February 1, 2026 (policy CS 404.2), the personal allowance is $20,748 per year for each parent. That figure changes with each year's tables.

What is left is each parent's income available for child support (ARM 37.62.116). The two figures are added together, and each parent's figure is divided by the total. The result is that parent's share of the child's needs (ARM 37.62.118(1)).

The Primary Child Support Allowance and Supplements

The child's basic needs are represented by the primary child support allowance. It is "a standard amount to be applied toward a child's food, shelter, clothing and related needs and is not intended to meet the needs of a particular child" (ARM 37.62.121). The allowance is 30% of the personal allowance for the first child, with 20% added for each of the second and third children and 10% for each child after that. In the tables effective February 1, 2026, that is $6,224 per year for one child.

The allowance is then supplemented by costs specific to your children (ARM 37.62.123(1)):

• reasonable child care costs a parent incurs as a prerequisite to employment, reduced by the federal dependent care tax credit;
• the actual cost of adding the children to a health insurance policy, or of a child-only policy;
• unreimbursed health care expenses for a child that exceed $250 per year and are recurring and predictable; and
• other needs of the child as determined by the circumstances of the case.

The total is divided between the parents by their shares, and each parent receives credit for the supplemental costs that parent actually pays (ARM 37.62.123(2), (3)). See medical support and health insurance for children.

The Standard of Living Adjustment

If a parent still has income available after covering that parent's share of the allowance and supplements, the remainder is subject to a standard of living adjustment, called SOLA. Its stated purpose is "to ensure that the child enjoys, to the extent possible, the standard of living commensurate with the parent's income" (ARM 37.62.128(1)). The remaining income is multiplied by a factor that depends on the number of children. For one child the factor is .14 (ARM 37.62.128(3)).

When a parent or child travels more than 2,000 miles in a calendar year to carry out the parenting plan, the guidelines reduce the income subject to SOLA by transportation costs above a standard amount (ARM 37.62.130).

Low Income and the Minimum Contribution

The guidelines call for a specific minimum contribution in two situations: when a parent's income after deductions is at or below the personal allowance, and when the calculated obligation is less than 12% of income after deductions (ARM 37.62.126(1)). In the first case the minimum is found from a sliding table in the rule. In the second it is 12% of income after deductions. These minimums are presumptive and may be rebutted by the circumstances of the case with an appropriate finding (ARM 37.62.126(2)).

Parenting Days and the Transfer Payment

Each parent now has a total annual support amount. The last step allocates those amounts by where the child lives. If the children live primarily with one parent and spend no more than 110 days a year with the other, the transfer payment is simply the other parent's total (ARM 37.62.134(2)(a)). If a child spends more than 110 days a year with both parents, each parent keeps the portion for the child's time in that parent's home and owes the rest, and the lower amount is subtracted from the higher (ARM 37.62.134(2)(b)). Our page on parenting time and child support explains this step.

The annual result is divided by 12 and rounded to whole dollars. A court can depart from that bottom line only with the findings described in our child support overview. If a parent is self-employed, the income step takes more work, and our page on self-employed parents covers it.

This page explains Montana law in general as of the 2025 Montana Code Annotated and the current Montana Child Support Guidelines. It is not legal advice about your specific case.