Child support · MT
Montana child support calculator
The Montana guidelines worksheet run on an annual figure, from the personal allowance to the 110-day parenting rule.
Rules read on official Montana pages on · Checked by Radif Partners · How we calculate
- Model
- Melson formula
- Income counted
- Net income
- Shared parenting
- No fixed formula
- 1 child, $5,000 / $3,000
- $779
- a month
With $4,000 a month of income after deductions, against $2,000 for the other parent and one child living with that parent, the Montana guidelines give about $716 a month for 2026. Montana does not publish a support chart. The Child Support Services Division (CSSD) works on yearly amounts in a Melson-type sequence set by ARM 37.62. Each parent first keeps a personal allowance of $20,748 a year, equal to 1.3 times the federal poverty guideline for one person. What is left is the income available for support, and its split between the parents fixes who carries what share of the primary allowance: $6,224 a year for one child, $10,374 for two, plus child care and the children's premium. Above that, a standard of living adjustment of 14.000% for one child, rising to 47% for eight or more, is applied to whatever income still remains. The CSSD tables behind these figures took effect on February 1, 2026.
Guideline child support in Montana, per month
$779
$9,348 a year
| Income after deductions minus personal allowance (paying parent, a month) | $3,271 |
| Paying parent’s share of income available | 72.0% |
| Primary allowance and supplements, 1 child (a month) | $519 |
| Standard of living adjustment factor | 14.0% |
| Paying parent’s gross annual support, a month | $779 |
Estimate under the Montana guideline as published, from the incomes you enter. Deviations, imputed income, other children and the judge's findings can change the order. How this is calculated.
Why the Montana worksheet starts from a yearly figure
ARM 37.62.101 sets the guideline on an annual basis and turns the result into twelve equal payments only at the end. So the inputs are yearly: a parent with $4,000 a month after taxes and other allowed deductions enters $48,000 on line 3 of Worksheet A, and the other parent $24,000. The deductions themselves are broad: federal and state income tax, FICA and Medicare, mandatory retirement, ordered alimony and support for other children all come off before anything else. The calculator above expects that after-deduction figure, not gross pay.
The personal allowance of $20,748 then comes off each income. In our example the higher earner keeps $27,252 of income available and the other parent $3,252, which puts 89.339% of the child's primary allowance and supplements on the higher earner. CSSD reprices the allowance every year from the poverty guideline, which is why a Montana order computed in 2025 does not match one computed today on the same pay.
The 12 percent floor and the minimum contribution
Line 6 of Worksheet A sets a floor for every parent: 12% of income after deductions when some income is available, or, for a parent at or below the personal allowance, a slice taken from the income-ratio table of ARM 37.62.126. A parent with $1,500 a month after deductions has a ratio of 1 to the allowance, which calls for a multiplier of 9%: $135 a month. Below a ratio of 0 the minimum is zero.
Parenting days and the 110-day line
Montana counts days, not overnights: a day is the larger part of a 24-hour calendar period. Up to 110 days a year with the other parent, nothing changes. Once a child spends more than 110 days in each home, Worksheet B reduces each parent's obligation by 0 for every day above 110 and offsets the two results. With 146 days for the higher earner, the payment in our example drops from $716 to $479 a month. Two children with the same incomes cost $1,088, since the SOLA factor climbs to 21%.
The worksheets and the yearly tables are published by the DPHHS Child Support Services Division. For another Melson-type state with a different structure, compare Hawaii.
The Montana guideline this calculator applies
| Rule | Montana |
|---|---|
| Model | Melson-type formula: personal allowance, primary child support allowance, supplements and standard of living adjustment (ARM 37.62.101-148) |
| Income counted | Net income: after income taxes and mandatory deductions, as the state defines it. |
| Shared parenting | No overnight formula in the calculator (see the rule below) |
Monthly support for one paying parent, the other parent without income
| Paying parent’s monthly income | 1 child | 2 children | 3 children | 4 children |
|---|---|---|---|---|
| $2,000 | $271 | $272 | $270 | $272 |
| $3,000 | $624 | $950 | $1,227 | $1,272 |
| $4,000 | $764 | $1,160 | $1,497 | $1,660 |
| $5,000 | $904 | $1,370 | $1,767 | $1,968 |
| $6,000 | $1,044 | $1,580 | $2,037 | $2,280 |
| $8,000 | $1,324 | $2,000 | $2,577 | $2,900 |
| $10,000 | $1,604 | $2,420 | $3,117 | $3,520 |
| $12,500 | $1,954 | $2,944 | $3,792 | $4,292 |
| $15,000 | $2,304 | $3,470 | $4,467 | $5,068 |
| $20,000 | $3,004 | $4,520 | $5,817 | $6,620 |
How the amount is set. For each parent: income available = income - deductions (ARM 37.62.110) - personal allowance (ARM 37.62.116). Parental share = own income available / combined income available (ARM 37.62.118). Each parent owes its share of the primary child support allowance plus supplements (child care net of the federal dependent care credit, children's health insurance, recurring unreimbursed medical costs over $250 per child per year, other needs) (ARM 37.62.121, .123). SOLA = (income available - share of primary allowance and supplements, not below 0) x SOLA factor (ARM 37.62.128). Total support amount = share of primary allowance with supplements + SOLA, or the minimum support obligation if applicable (ARM 37.62.134(1)). Annual transfer payment / 12, rounded to whole dollars per child ($0.50 rounds up) (ARM 37.62.134(2)). Worksheet A (CSSD, rev. 2025-08-12): line 6 = 12% of income after deductions (or the WS-C minimum when income available is 0); line 7 = higher of income available and line 6, used for the parental share; line 16 = lower of share of need and income available; line 22 = higher of (line 16 + SOLA) and line 6; line 24 = line 22 minus expenses paid. source
Income. Income includes actual income from any source (wages, tips, commissions, bonuses, profits, dividends, pensions, retirement distributions, interest, trust income, royalties, alimony, social security, veterans', workers' compensation, unemployment and disability benefits, earned income credit, net capital gains) and imputed income; self-employment income is gross receipts minus reasonable and necessary expenses (ARM 37.62.105). Allowable deductions under ARM 37.62.110 (CSSD Worksheet A lines 2a-2k: ordered support and allowance for other children, alimony, federal and state income tax, FICA and Medicare, mandatory retirement, required employment expense, dependent care for other children) (including support for other children: one-half of the primary allowance for other children without an order) and the personal allowance (ARM 37.62.114) are subtracted to get income available for child support (ARM 37.62.116). Guidelines are computed on an annual basis, paid in equal monthly installments (ARM 37.62.101(3)). The calculator input is income after these deductions (Worksheet A line 3).
Parenting time. No adjustment when the child spends no more than 110 days a year with the other parent. When any child spends more than 110 days with both parents (or children live primarily with different parents), each child's need is recalculated, each parent keeps the share for the days the child is with him or her and owes the share for the days with the other parent, and the obligations are offset per child (ARM 37.62.124, 37.62.134(2)(b)). A 'day' is the majority of a 24-hour period (ARM 37.62.124(3)). Worksheet B part 2 applies a credit factor of 0.0069 per day above 110 to each parent's per-child obligation, then offsets (CSSD worksheets, https://dphhs.mt.gov/assets/cssd/GuidelineWorksheetsandInstructions.pdf).
Child care and health care. Reasonable work-related child care, reduced by the federal dependent care tax credit, supplements the primary allowance and is shared by parental share; each parent is credited for supplements it pays (ARM 37.62.123). The cost of adding the children to a policy (or a child-only policy) and recurring unreimbursed health costs over $250 per child per year supplement the primary allowance (ARM 37.62.123(1)(b)-(c)). Supplements to the primary allowance are divided by parental share (ARM 37.62.123).
Low incomes. Personal allowance of $20,748 per year (2026) is deducted from each parent's income (ARM 37.62.114; CS 404.2). A minimum contribution applies when income after deductions is at or below the personal allowance (income-ratio table, 0% to 11%) or when the calculated obligation is below 12% of income after deductions (ARM 37.62.126).
Worth knowing in Montana
- CSSD updates the guideline tables every year to follow the federal poverty guidelines and the IRS mileage rate; the 2026 tables took effect February 1, 2026 (CS 404.2). source
- The personal allowance is 1.3 times the federal poverty guideline for one person: $20,748 a year in 2026 (ARM 37.62.114; CS 404.2). source
- Montana guidelines are computed annually and paid in equal monthly installments (ARM 37.62.101(3)). source
- The next quadrennial guidelines review is to be completed in December 2028 by the Guidelines Review and Oversight Committee (GROC) (MCA 40-5-209). source
- A long distance parenting adjustment uses the IRS business mileage rate ($0.725/mile) and a standard expense of $1,450 (ARM 37.62.130; CS 404.2). source