Montana Child Support Calculator

Montana child support starts from each parent’s income after taxes and other deductions. Each parent keeps an amount for their own living costs, pays a share of a set yearly amount for the children’s basic needs, and adds a percentage of the income they have left. For one child and incomes after deductions of $4,000 and $2,000 a month, the higher earner pays about $716 a month when the child lives with the other parent.

Each amount subtracts estimated 2026 taxes from both parents’ pay, as the calculator above does. In 2026, Montana sets the yearly cost of the children’s basic needs (the primary child support allowance) at $6,224 for one child, $10,374 for two, and $14,523 for three. Both parents share this cost. The 2026 figures are in CSSD’s guidelines tables. CSSD updates them every February, and the next update is expected February 1, 2027.

Montana uses a version of the Melson formula. First, each parent keeps an amount to live on. Next, the parents split the cost of the children’s basic needs by income. Then each parent adds a percentage of the income they have left.

The rules are in the Montana child support guidelines, ARM 37.62, and the steps follow the CSSD worksheets:

1. Find each parent’s income after deductions. Add up yearly income from all sources. Then subtract income taxes, Social Security and Medicare, required retirement contributions, court-ordered support the parent pays for other children, required work expenses, and an amount for other children who live with the parent.
2. Subtract the personal allowance ($20,748 a year), the amount each parent keeps to live on.
3. Find each parent’s share of the income both parents have left after their allowances.
4. Split the children’s needs: the primary child support allowance plus child care and health costs, divided by each parent’s share of income.
5. Add the standard of living adjustment (SOLA): a percentage of the income each parent still has left, from 14% for one child to 47% for eight or more. This lets the children share in each parent’s standard of living.
6. Check the minimum each parent must pay, then adjust for the days the children spend with each parent.

Example

One parent has income after deductions of $48,000 a year and the other has $24,000. After each subtracts the personal allowance, they have $27,252 and $3,252 left. The higher earner’s share of the $6,224 primary allowance is $5,560, and the standard of living adjustment adds $3,037. With the child living with the other parent, that comes to about $716 a month.

Yes, once a child spends more than 110 days a year (about 30%) with each parent. Then each parent’s amount goes down for every day above 110 that the child spends with them, and the parent who still owes more pays the difference. For example, with one child and incomes after deductions of $4,000 and $2,000 a month, the higher earner pays about $716 a month with 110 days or fewer, $651 at 120 days, $479 at 146, and $238 at equal time.

Montana’s worksheet B lowers each parent’s amount by 0.69% for every day over 110 that the child spends with that parent. The parent who still owes more pays the difference. See ARM 37.62.124 and 37.62.134 and the worksheet B instructions.

A day counts for the parent who has the child for most of it, midnight to midnight unless the parents or the court set other hours. Time the child spends in school or day care counts for the parent who is the main contact for it. Each child’s days are counted separately.

Montana adds child care a parent needs in order to work to the children’s needs, after subtracting the federal child care tax credit. The parents split that cost by income, and each parent gets credit for the child care they already pay.

For example, if child care costs $600 a month after the tax credit and you have two thirds of the parents’ combined income left after their allowances, your share is $400, under ARM 37.62.123.

Montana adds two health costs to the children’s needs and splits them by income: the cost of adding the children to health insurance, and their regular medical costs that insurance doesn’t cover, above $250 a year per child. The parent who pays these costs gets credit for them.

• Premium: only the cost of adding the children to a policy, or of a policy that covers only the children, counts, under ARM 37.62.123.
• Reasonable cost: in its cases, CSSD treats coverage as affordable when it costs no more than 5% of the parent’s gross income (pay before taxes), under its medical support policy.

If the children live with you and you get TANF (cash assistance), you have to help the state get child support from the other parent, for example by naming them and going to paternity tests and court dates. The state keeps the support it collects, except up to $100 a month it passes on to you. Food stamps (SNAP) don’t require this.

• TANF: up to $100 of the support collected for the current month is passed on to your family and doesn’t lower your TANF check, under MCA 53-4-260. Past-due support isn’t passed on.
• Food stamps (SNAP): Montana doesn’t require you to help with child support to get SNAP, according to the USDA SNAP State Options Report.

If helping could put you or your children in danger, you can ask to be excused (Montana calls this good cause). The Montana child support guide has more on benefits and child support.

In 2026, each parent keeps $20,748 a year ($1,729 a month) for their own living costs. Montana calls this the personal allowance. A parent whose income after deductions is at or below that amount pays 0% to 11% of that income, with the percentage rising as income rises. A parent with more income pays at least 12%.

• At or below the allowance: the percentage rises with income, from 0% at a quarter of the allowance or less to 11% just under it. At $1,500 a month, it is 9%, or about $135 a month.
• Above the allowance: support is at least 12% of the parent’s income after deductions.
• Earning less than they could: support can be based on what a parent could earn, judged by their work history, skills, health, and local jobs, under ARM 37.62.106.

A judge can set a different minimum after explaining why on the record, under ARM 37.62.126. The allowance is 130% of the federal poverty guideline for one person and changes each year.

No. Montana has no income cap. After subtracting their allowance and their share of the children’s needs, including child care and health costs, each parent also pays 14% (one child) to 47% (eight or more) of whatever income they have left, however high it is.

The percentages are 14% for one child, 21% for two, 27% for three, 31% for four, 35% for five, 39% for six, 43% for seven, and 47% for eight or more, under ARM 37.62.128.

Yes. A judge, or the Child Support Services Division (CSSD) in its own cases, can order a different amount after explaining in writing why the guideline amount would be unfair or wrong for the family.

The written explanation must state the guideline amount and consider what is best for the children. Parents can agree to a different amount only in writing. The agreement must state the guideline amount and the reason for the different amount, and a court or CSSD must approve it, under ARM 37.62.102.

Ask the Child Support Services Division (CSSD) to review your order, or file a motion in district court. CSSD reviews an order after 36 months, or sooner after a big change, and changes it if the new amount differs by 15% or more. Keep following the current order until it changes.

• Through CSSD: ask for a review. A review can start before 36 months if either parent’s gross income changed by at least 30%, under CSSD’s review policy.
• Through the court: the Montana Judicial Branch has child support forms.

The Montana child support guide walks through each step.

Montana has no online calculator. Its official tool is the Montana Child Support Guidelines Worksheets and Instructions from the Child Support Services Division, used with the guidelines tables it updates each year.

Fill in the Montana Child Support Guidelines Worksheets and Instructions with the current guidelines tables. They work with yearly income and round support for each child, so a monthly calculation can come out a few dollars different.