Child support in Montana.
What the state’s own guideline says, where the number comes from, and the one figure that moves it more than anything you will argue about.
See a different stateMontana
Montana works from the bottom up rather than from a table. Each parent first keeps a 'personal allowance' — 1.3 times the federal poverty guideline for one person — to cover their own basics. What is left is each parent's income available for support. A 'primary child support allowance' for the children is set as a percentage of that personal allowance and split between the parents by income share. Then, if a parent still has income left over, a Standard of Living Adjustment (SOLA) adds a slice of it so the children share the parent's standard of living.
How Montana works out the number
Authority: Admin. R. Mont. Title 37, ch. 62, subch. 1 (ARM 37.62.101–37.62.148), promulgated under Mont. Code Ann. § 40-5-209 and applied under §§ 40-4-204, 40-5-226 and 40-6-116Montana counts days, not overnights, and the number is 110. 'When the child resides primarily with one parent and does not spend more than 110 days per year with the other parent, there is no adjustment to the transfer payment due. When at least one child spends more than 110 days per year with both parents, however, or when at least one child resides primarily with each parent, the transfer payment is adjusted.' A 'day' is 'the majority of a 24-hour calendar period in which the child is with or under the control of a parent'; when a child is at school or day care, the day belongs to whichever parent is the primary contact for that provider, and genuinely disputed days are split evenly.
Use the state’s own calculator, not ours
Montana publishes this itself, free. It is called Montana Child Support Guidelines Worksheets and Instructions, plus the Financial Affidavit and the annually republished guideline tables. ARM 37.62.148 requires. We are not going to build a competing calculator and ask you to trust it — this is the one a judge will recognize.
Open the Montana calculator →What goes into the calculation
What counts as income
ARM 37.62.105 counts 'economic benefit from whatever source derived,' listing salaries, wages, tips, commissions, bonuses, earnings, profits, dividends, severance, pensions, retirement distributions, draws or advances, interest, trust income, annuities, royalties, alimony, Social Security, veteran's, workers' comp, unemployment, disability, earned income credit and other government benefits, plus capital gains net of losses. Non-cash benefits count too — 'in-kind compensation, personal use of vehicle, housing, payment of personal expenses, food, utilities.' Self-employment is 'gross receipts minus reasonable and necessary expenses required for the production of income'; straight-line depreciation is allowed if the asset produces income, and 'a net loss in the operation of a business or farm may not offset other income' unless the businesses are related. On overtime and second jobs, ARM 37.62.105(5) is explicit: 'If overtime is mandatory and the worker has no control over whether or not overtime is worked, the overtime earnings are included in income for child support. In the case of voluntary overtime earnings or earnings from a job that is in addition to a full-time job, and the earnings are expected to continue for the foreseeable future, the earnings are presumed to be available for child support and are included in the calculation subject to rebuttal of the presumption.'
When a judge can treat you as earning more
'It is presumed that all parents are capable of working at least 40 hours per week at minimum wage, absent evidence to the contrary.' Income may be imputed when a parent is unemployed, underemployed, fails to produce sufficient proof of income, has unknown employment status, or is a student. 'Underemployed' is defined as working less than full time when full-time work is available locally, or earning less than the parent has earned before or is qualified to earn when better-paying jobs are available locally. The court weighs residence, work and earnings history, qualifications, local job opportunities and earning levels, age, literacy, health, criminal record, record of seeking work, and employers willing to hire. Income is NOT imputed if child care costs would offset it, if the parent is disabled to the point of being unable to earn or 'is incarcerated for more than 180 days,' if a dependent's unusual needs require the parent at home, if the parent has made diligent efforts to find work to no avail, or if the court finds imputation inequitable.
If you do not earn much
The personal allowance is the floor: 1.3 times the federal poverty guideline for a one-person household, deducted before support is computed. On top of that, ARM 37.62.126 sets a minimum contribution 'in all cases when the parent's income, after deductions, is less than or equal to the parent's personal allowance or the parent's calculated child support obligation is less than 12% of that parent's income after deductions.' Where income after deductions exceeds the personal allowance, the minimum is 12% of income after deductions. Below the personal allowance, a table converts an 'income ratio' into a multiplier: at a ratio of 0.00 to 0.25 the minimum contribution is zero, and it climbs by one percentage point at a time up to 0.11 for ratios just under 1.00. These minimums are presumptive and rebuttable with a finding on the record.
Childcare and health insurance
Both are 'supplements' added to the primary child support allowance and 'divided proportionately between the parents according to the parental share,' with each parent credited for what they actually pay. Child care must be 'reasonable child care costs incurred by a parent for children of the calculation as a prerequisite to employment,' reduced by the federal dependent care tax credit. Health insurance counts only as 'the actual cost of adding the children to an existing health insurance policy or the cost of a child-only policy' — not the whole family premium.
Private school, special needs, activities
Supplements also include 'unreimbursed health care expenses for each child of the calculation that exceed $250 per year and are recurring and predictable,' and a catch-all for 'other needs of the child as determined by the circumstances of the case.' Long-distance parenting gets its own rule: once a parent's or child's travel exceeds 2,000 miles in a calendar year, the excess (valued at the IRS business mileage rate, plus non-automobile transportation) reduces that parent's income available for SOLA. Only transportation counts — 'Expenses are limited to costs of transportation and do not include meals, lodging, or other costs.'
When a judge can depart from the number
The guidelines create a presumption. To depart, 'the decree, separation order, or support order contains a specific written finding showing justification that application of the guidelines would be unjust or inappropriate, based upon evidence sufficient to rebut the presumption,' and the findings 'must include a statement of the amount of support that would have been ordered under the guidelines without the variance.' A variance by agreement must be in writing, free of coercion, contain specific justification, state the guideline amount, and be approved. If a variance rests on some condition or act, the order must provide that support snaps back to the guideline amount when that condition ends.
Two things surprise people. First, Montana does not use an income-shares table at all — it is a Melson-formula state, so each parent is guaranteed a personal allowance of 1.3 times the poverty line before any support is computed, and the children then get a share of what is genuinely left over. That makes Montana orders behave very differently from a neighboring state's at the same income. Second, ARM 37.62.140 requires you to plan ahead: 'If any material change in current circumstances is anticipated within 18 months, separate child support calculations must be completed,' and the order is written so the future number takes effect automatically. If you know a job change or a child's day care ending is coming, raise it now rather than filing a modification later.
Later on
When it ends
Mont. Code Ann. § 40-4-208(5): 'provisions for the support of a child are terminated by emancipation of the child or the child's graduation from high school if the child is enrolled in high school, whichever occurs later, but in no event later than the child's 19th birthday, unless the termination date is extended or knowingly waived by written agreement or by an express provision of the decree.'
College and support after 18
Only two routes. By written agreement or an express provision in the decree extending the termination date (§ 40-4-208(5)); or for disability — support for a child with a disability who is financially dependent on the custodial parent and for whom that parent is the primary caregiver 'continues until the court finds that the individual is no longer disabled or is no longer financially dependent on the custodial parent,' for decrees issued on or after July 1, 2019 or in effect on that date. A parent whose order was terminated before July 1, 2019 solely because a disabled child turned 19 can petition to reinstate it. There is no general college-support power.
Changing the amount later
Mont. Code Ann. § 40-4-208(2)(b): where the decree contains support provisions, it may be modified only 'upon 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 of Public Health and Human Services in a Title IV-D case (and in that last route, not within 12 months of the order or last modification). Where the decree has no support provisions at all, modification may only be made within 2 years of the decree. A missing or violated medical support order justifies immediate modification.
How far back a change can reach
Mont. Code Ann. § 40-4-208(1): 'a decree may be modified by a court as to maintenance or support only as to installments accruing subsequent to actual notice to the parties of the motion for modification.' Nothing before notice.
If someone stops paying
ARM 37.62.142 requires support to be paid in U.S. dollars and gives no credit for gifts, clothing, food, or paying expenses in lieu of dollars except by court or administrative order. 'Direct payments to the child, the parent or a third party will not be allowed as credit for payment of a child support obligation payable through the clerk of court, the Child Support Services Division or other entity specified in the court or administrative order.' We did not confirm Montana's official license-suspension or interest rules.
What we could not confirm
- The rule text we relied on is the Child Support Services Division's own reformatted copy of the rules, dated April 2023, and that copy itself says the only official version lives on the Montana Secretary of State's rules website, which we could not read. Check rules.mt.gov (Department 37, Chapter 62) for any change since 2023. We also could not confirm Montana's official enforcement tools such as license suspension or interest on arrears.
- 1 official page we tried to read refused automated access. We did not try to get around the block, so some detail above comes from a different official source rather than the one we would have preferred.
Compare all fifty states
The overnight thresholds, the ending ages and the college rules, side by side.
The rest of what we have written about Montana. Every figure is quoted from Montana’s own statute or its courts’ own published schedule, and carries the date we last checked it.