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Montana child support: personal allowance, SOLA, the 110-day rule, and a worked example

Montana uses a Melson-style formula that runs in three layers. Each parent first keeps a personal allowance, then the parents share the children's primary needs by income, and finally each parent adds a percentage of whatever income is left, the standard of living adjustment, or SOLA. The Child Support Services Division updates the dollar figures every February.

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At a glance

ModelMelson formula: personal allowance, primary child support allowance, then SOLA (ARM 37.62.101 to 148)
Personal allowance$20,748 a year per parent since February 1, 2026 (1.3 x the poverty guideline)
Primary allowance$6,224 a year for one child, $10,374 for two, $14,523 for three
SOLA factor14% of remaining income for one child, 21% for two, 27% for three, up to 47% for eight or more
Minimum contribution12% of income after deductions when income exceeds the personal allowance
Shared parentingMore than 110 days a year with each parent: Worksheet B credit of 0.69% per day over 110
Support endsEmancipation or high school graduation, whichever is later, but no later than age 19

The three layers of Montana's worksheet

Worksheet A starts with each parent's total income, including wages, self-employment earnings, pensions and Social Security, unearned income, imputed income and the earned income tax credit. It subtracts ordered support and an allowance for other children, ordered alimony, actual federal and state income taxes, FICA and Medicare, mandatory retirement contributions and required employment expenses. The result is income after deductions.

Layer one: each parent subtracts the personal allowance, $20,748 a year in 2026, to find income available for child support. The parents' shares of the combined available income set how the children's needs are divided. Layer two: the primary child support allowance ($10,374 a year for two children) plus actual child care, the children's health insurance premium, and recurring uninsured medical costs above $250 per child become the children's total needs, split by those shares.

Layer three: whatever each parent has left after their share of the children's needs is multiplied by the SOLA factor, 21% for two children, so the children share in a higher standard of living when a parent can afford it. A parent's annual support is their share of the needs plus their SOLA amount, but never less than the 12% minimum contribution.

Worked example: Montana

  1. After deductions and the $20,748 personal allowance, Parent A has $48,000 a year available for child support ($4,000 a month) and Parent B $32,000 ($2,667 a month). Parent A's share is 60%.
  2. With no child care or insurance costs, the children's total needs are the $10,374 primary allowance for two children. Parent A's share of that is about $6,224 a year, leaving roughly $41,776 of available income for SOLA.
  3. At 21% for two children, Parent A's SOLA is about $8,773, so Parent A's annual support is about $14,997: $1,250 a month. Seen across both parents, Montana's layers here add up to the same thing as splitting $2,083 a month by income.
  4. That is about $15,000 a year if the children live mainly with Parent B. CoreParent's calculator runs these Worksheet A layers with the 2026 tables, but it estimates income after deductions from gross pay, so confirm its figure with the CSSD worksheets.

This is an estimate, not legal advice. Figures are rounded to the dollar and leave out the insurance, childcare, and other adjustments your case may have. Try your own numbers in CoreParent's calculator, then confirm with the state's official calculator.

The 110-day rule and Worksheet B

Montana counts days, not overnights: a day is the majority of a 24-hour period, midnight to midnight unless the parents or court define it differently, and during school or day care the child is with the parent who is the main contact. When a child spends more than 110 days a year with each parent, Worksheet B applies. Each parent's obligation for that child is reduced by 0.0069 for every day over 110 the child spends with that parent, the two reduced amounts are offset, and the payment cannot exceed the payer's unreduced obligation.

In the example, with 130 days a year with Parent A, Parent A's payment drops to about $963 a month instead of $1,250. With an even split, both obligations are cut roughly in half and Parent A pays about $208. Worksheet B also handles split custody, where each parent has at least one child.

Child care, health insurance and medical costs

Child care needed for a parent's employment, reduced by the federal dependent care tax credit, is added to the primary allowance. So are the premium a parent actually pays to cover the children and uninsured medical costs above $250 per child per year that are recurring and predictable. Other special needs, and private school or similar costs if the parents agree, can be added too. Each parent is then credited for the supplemental costs they pay directly.

Low incomes: the minimum contribution

A parent whose income after deductions is above the personal allowance owes at least 12% of income after deductions. A parent whose income is at or below the allowance owes a minimum contribution from a sliding table (Worksheet C) based on how income compares with the allowance, so low earners still contribute something in proportion to what they have.

Other children and long-distance parenting

Support a parent is ordered to pay for other children is deducted, and for other children the parent is legally obligated to support there is an allowance from the CSSD table: $3,112 a year for one, $5,187 for two. When travel to carry out the parenting plan is long, Worksheet D reduces the traveling parent's income available for SOLA using the IRS business mileage rate, 72.5 cents a mile in the 2026 tables.

When support ends

Child support ends at emancipation or high school graduation if the child is enrolled, whichever is later, but no later than the 19th birthday, unless a written agreement or the decree extends it. Since July 1, 2019, support for a child with a disability who remains financially dependent on the custodial parent, and whose primary caregiver is that parent, does not end solely because of age.

Modification

A decree with support terms can be modified on changed circumstances so substantial and continuing as to make the terms unconscionable, by written consent, or on application by the Department when it provides child support services. Except in limited cases, no modification may be made within 12 months of the last order, and changes apply only to payments falling due after notice of the motion. A missing or violated medical support order justifies immediate modification.

The agency

The Child Support Services Division of the Montana Department of Public Health and Human Services adopts the guidelines by rule, reviews them every four years, publishes the yearly tables each February, and uses the same worksheets courts and parents use.

Documents you will need

Montana child support FAQ

How is child support calculated in Montana?

Each parent's income after deductions, minus a $20,748 personal allowance, sets their share of the children's needs (the primary allowance plus child care and medical costs). Each parent then adds a SOLA percentage of their remaining income, with a 12% minimum contribution.

What is the SOLA in Montana child support?

The standard of living adjustment: a percentage of the income a parent has left after their share of the children's needs, 14% for one child, 21% for two and 27% for three.

How much is child support for 2 kids in Montana?

In our example, a parent with $48,000 a year available after the personal allowance, against $32,000 for the other parent, pays about $1,250 a month before any shared parenting credit.

How many days change child support in Montana?

More than 110 days a year with each parent. Each parent's obligation then falls 0.69% for every day over 110 with that parent, and the two are offset.

When does child support end in Montana?

At emancipation or high school graduation, whichever is later, but no later than 19, unless an agreement or the decree says otherwise or the child has a qualifying disability.

Next steps

Sources

Verified against these official sources in October 2026:

Child support in every other state

All states

This is general educational information, not legal advice, and official figures change. Last verified: October 2026. Consult a licensed family-law attorney in Montana.