Montana Child Support Laws (2026): Guidelines & Calculator

Montana calculates child support under the Modified Melson Formula, one of only three states in the country to use this three-stage model. The formula is governed by Administrative Rules of Montana (ARM) 37.62 and Montana Code Annotated (MCA) 40-4-204. Use the Montana child support calculator below to estimate a guideline amount, or open the full-page Montana child support calculator to run detailed scenarios.

Overview of Montana Child Support Laws

Montana child support laws ensure both parents share the financial responsibility of raising their children, regardless of whether the parents were married. The Montana Department of Public Health and Human Services (DPHHS) administers child support services through its Child Support Services Division (CSSD).

CSSD provides several core services to Montana families:

• Locating absent parents
• Establishing paternity
• Establishing and modifying child support orders
• Establishing medical support orders
• Enforcing child support obligations
• Collecting and distributing payments

To apply for child support services, visit your local Child Support Services office or call the statewide number at (800) 346-5437.

All child support orders in Montana must include a provision for medical support. Health insurance coverage for the child is part of every support order by law.

Establishing Paternity in Montana

Before a court can issue a child support order, legal paternity must be established. Montana law requires both parents to support their children, regardless of marital status.

Paternity can be established in Montana through several methods:

• Voluntary acknowledgment: Both parents sign a paternity acknowledgment form at the hospital after birth or later through the vital records office
• Court adjudication: A judge reviews evidence and makes a legal determination of paternity
• Genetic testing: DNA testing provides conclusive proof of biological parentage, with accuracy rates exceeding 99%
• Presumed paternity: Under Montana law, a child born during a marriage or within 300 days after a divorce, death, or annulment is presumed to be the husband's child

Montana maintains a Putative Father Registry to help identify and locate biological fathers. You can search the registry or register through DPHHS Vital Records.

Once paternity is established, the court can move forward with calculating and ordering child support.

How Child Support Is Calculated in Montana: The Modified Melson Formula

Montana uses the Modified Melson Formula to calculate child support, governed by ARM 37.62 and MCA 40-4-204. Montana adopted this three-stage model in 1992, moving away from a pure income-shares approach. Delaware and Hawaii are the only other states that use this framework.

The Modified Melson Formula differs from the standard Income Shares model in a key way: it first protects each parent's basic subsistence needs before allocating support, and it then adds a third stage that shares any remaining parental income with the child so the child's standard of living rises along with the parents' prosperity.

The amount determined under the guidelines is presumed adequate and reasonable. A court may deviate only if it finds by clear and convincing evidence that applying them would be unjust to the child or to either parent.

Stage 1: Personal Allowance (Self-Support Reserve)

Before any support obligation is calculated, each parent receives a personal allowance under ARM 37.62.114. This allowance is set at 1.3 times the federal poverty guideline for a one-person household. For 2026, the personal allowance is $20,748 per year (updated February 1, 2026). This amount is deducted from each parent's gross income first, ensuring that both parents can meet their own basic living needs before being required to contribute to child support.

The DPHHS updates this figure annually to reflect current federal poverty guidelines.

Stage 2: Primary Child Support Allowance

After the personal allowance is deducted, the parents' remaining income is combined and used to determine the primary child support allowance under ARM 37.62.121. This allowance is set at 0.30 multiplied by the personal allowance for one child. For 2026:

Each parent's share of the primary allowance is proportional to their share of the combined income available for support.

Stage 3: Standard of Living Adjustment (SOLA)

The third stage distinguishes Montana's formula from most other states. Under ARM 37.62.128, after the primary child support allowance is covered, any remaining income available to each parent is subject to the Standard of Living Adjustment (SOLA). The purpose of SOLA is to ensure that the child enjoys, to the extent possible, the standard of living commensurate with the parent's income.

SOLA is calculated by taking each parent's remaining income after the primary allowance is satisfied and multiplying it by a percentage based on the number of children:

Income Determination Under ARM 37.62.105

Montana defines income broadly for child support purposes. Under ARM 37.62.105, gross income includes:

• Wages, salaries, and tips from all employment
• Commissions and bonuses
• Self-employment income (after legitimate business expenses but before personal income taxes)
• Rental income (after reasonable operating expenses)
• Interest and dividends from investments
• Unemployment benefits and workers' compensation
• Retirement and pension benefits
• Social Security benefits
• Military allowances
• Trust income and annuities

Parents are presumed capable of working full-time (40 hours per week). If a parent is voluntarily unemployed or underemployed, the court may impute income at minimum wage for 40 hours per week under ARM 37.62.106. Income cannot be imputed if the parent has made a diligent effort to find suitable employment.

A new spouse's income is not counted when calculating child support. Stepparents have no legal obligation to support children from a previous relationship.

The Calculation Process

Here is a simplified overview of how Montana calculates child support:

1. Determine each parent's gross income from all sources
2. Subtract the personal allowance ($20,748/year for 2026) and other allowable deductions under ARM 37.62.110 including taxes and pre-existing support obligations
3. Calculate income available for child support for each parent
4. Determine each parent's percentage share of the combined available income
5. Apply the primary child support allowance from the table above, each parent paying their proportional share
6. Add supplemental amounts for health insurance premiums, work-related child care, and other qualifying expenses under ARM 37.62.123
7. Apply SOLA on each parent's remaining income at the applicable percentage
8. Adjust for parenting time if the non-custodial parent has the child more than 110 days per year

Worksheets for Different Custody Arrangements

Montana provides different worksheets depending on the custody arrangement:

• Worksheet A: Used for standard parenting arrangements where one parent has primary custody
• Worksheet B: Used when at least one child resides more than 110 days per year with each parent, or when different children reside primarily with different parents (split custody)

A "day" is defined as the majority of a 24-hour calendar period during which the child is with or under the control of a parent.

When the non-custodial parent has the child for more than 110 overnights per year (roughly 30% of the year), a parenting time adjustment reduces the basic support obligation. This adjustment recognizes the increased direct costs the non-custodial parent bears during extended parenting time.

You can download the official guidelines packet, worksheets, and instructions from the CSSD Guidelines page.

Factors the Court Must Consider

Under MCA 40-4-204, the court must consider all relevant factors when setting support, including:

• The financial resources of the child
• The financial resources of both parents
• The standard of living the child would have enjoyed if the parents had remained together
• The physical and emotional condition of the child
• The child's educational and medical needs
• The age of the child
• The cost of child care
• Any existing parenting plan
• The needs of any other person the parent is legally obligated to support

Marital misconduct is not a factor in determining child support amounts.

Deviation from Guidelines

If the court determines the guideline amount is unjust or inappropriate, it must:

• State its reasons for the deviation
• Include the amount that would have been ordered under the guidelines
• Provide clear and convincing evidence supporting the deviation

Medical Support Orders in Montana

Under MCA 40-4-204 and Title 40, Chapter 5, Part 8, every child support order in Montana must include a medical support order. This is not optional.

Key requirements of medical support orders:

• A parent who has health insurance available at a reasonable cost through their employer must cover the children on that plan
• If both parents have health plans available, the court may order coverage from either or both parents
• Both parents may be required to share premiums, deductibles, and other out-of-pocket health care expenses
• Each order must require both parties to promptly file with the court their current health insurance information, including the carrier name, policy number, and names of covered persons

Uninsured medical expenses such as copays, prescriptions, and dental costs are typically divided between parents based on their respective income percentages.

How to Modify Child Support in Montana

Montana law allows parents to request a review of existing child support orders every 36 months after the order was established or last reviewed. No special reason is needed for a 36-month review.

To request a modification before 36 months have passed, a parent must demonstrate a substantial change in circumstances. Qualifying changes include:

• A change in the physical custody of the child
• A significant increase or decrease in child care or medical expenses
• New children requiring support from the obligor parent
• A 30% or greater change in either parent's income (increase or decrease)

Steps to Request a Modification

1. Contact the investigator assigned to your case at CSSD
2. Request a review packet from the investigator
3. Complete and return the packet with supporting documentation such as pay stubs, tax returns, or proof of changed circumstances
4. CSSD reviews the case and may issue a proposed modified order

If neither parent responds to a review notice, the court finalizes the order by default based on the terms in the notice. Pay close attention to all deadlines. If a review notice proposes terms you disagree with, ask a Montana family lawyer for a free case evaluation before the order is finalized by default (attorney advertising).

You can find modification forms on the Montana Courts website or call 1-800-666-6899 for assistance.

Key Modification Rules

• Either parent may request a modification
• A new spouse's income is not factored into the recalculation
• Stepparents are not obligated to support children from a previous relationship
• Under MCA 40-4-208(1), a court may modify support only as to installments accruing after actual notice to the parties of the motion for modification, so installments that accrue between filing and notice are not affected

Enforcement and Penalties for Non-Payment

The Child Support Services Division (CSSD) enforces child support orders using a variety of federal and state tools. Montana takes non-payment seriously, and the consequences escalate with the amount of arrears.

Income Withholding

Income withholding is the primary collection method in Montana. Unless the court grants a written exception, all child support orders are enforced through immediate income withholding. Employers must withhold the ordered amount from wages, bonuses, and salaries and send it to the State Disbursement Unit.

Tax Refund Interception

CSSD can intercept federal and state income tax refunds, federal salaries and wages, and federal retirement pay to apply toward arrears. This is an administrative process that does not require a separate court order.

Liens on Property and Bank Accounts

CSSD can place liens on real and personal property so the delinquent parent cannot sell or transfer assets without first paying the child support debt. The agency can also seize funds directly from bank accounts.

Credit Bureau Reporting

Past-due child support is reported to credit bureaus, which can affect the obligor's credit score and ability to obtain mortgages, loans, and employment.

License Suspension

If a parent's arrears total six months or more of support, CSSD can suspend:

• Driver's licenses
• Professional and occupational licenses
• Recreational licenses (hunting, fishing)

Licenses remain suspended until the parent makes satisfactory payment arrangements.

Passport Denial

Under federal law, if arrears exceed $2,500, the U.S. State Department will deny or revoke the obligor's passport. CSSD reports qualifying cases to the federal Office of Child Support Services for passport action.

Contempt of Court

Under Montana Code Annotated 40-5-601, if a parent fails to pay support as ordered, the receiving parent or their assignee can petition the court for a contempt finding.

Contempt penalties for each failure to pay include:

• Up to 5 days of incarceration in the county jail
• Up to 120 hours of community service
• Up to a $500 fine

The court's contempt order must include a provision allowing the obligor to purge the contempt by making payment.

A parent can defend against contempt charges by showing clear and convincing evidence of:

• Insufficient income to pay the arrears
• No personal or real property that can be sold to raise the needed amount
• Unsuccessful attempts to borrow from financial institutions
• No other available source of funds
• A valid out-of-court agreement with the payee modifying the obligation
• Some other reasonable basis for non-compliance

Contempt proceedings must be brought within 3 years of the last failure to comply with the support order.

Statute of Limitations for Arrears

Under MCA 27-2-201(3), the statute of limitations for collecting past-due child support that accrued after October 1, 1993, is:

• 10 years from the termination of the support obligation, OR
• 10 years from entry of a lump-sum judgment for arrears, whichever is later

The statute of limitations is paused when the obligor is out of state and cannot be served. The 10-year period restarts if the obligor acknowledges the debt in writing, makes a partial payment, or a court or administrative action is taken to enforce the debt.

When Does Child Support End in Montana?

Under MCA 40-4-208(5), child support in Montana terminates when the child:

• Turns 18, OR
• Graduates from high school if still enrolled, whichever occurs later
• But in no event later than the child's 19th birthday

This means if a child turns 18 in January but graduates high school in May, support continues until graduation. If the child does not graduate before turning 19, support ends at age 19 regardless.

Exception for Children with Disabilities

Child support does not automatically terminate based on age if the child has a disability that causes them to be financially dependent on the custodial parent. In these cases, the obligation continues until the court finds the individual is no longer disabled or no longer financially dependent on the custodial parent.

Multiple Children

If you are paying support for multiple children and one child reaches the age of majority or graduates high school, you should petition for a modification to adjust your support obligation downward. The obligation does not automatically decrease.

Emancipation in Montana

Under MCA 41-1-501, Montana allows a minor to petition for limited emancipation. Requirements include:

• The minor must be at least 16 years old
• The minor must be a Montana resident
• The minor must demonstrate the ability to support and manage their own affairs
• The minor must have graduated, be on track to graduate, or have earned a GED
• The court must find that limited emancipation is in the youth's best interests

A limited emancipation order requires the minor to check in with the court on a regular schedule. If the minor fails to comply, the court can revoke emancipation status.

Download emancipation petition forms from the Montana Courts website.

Termination of Parental Rights

Terminating parental rights does not automatically eliminate past-due child support obligations. Arrears that accrued before the termination remain enforceable.

Montana Child Support Guidelines Review

Under MCA 40-5-209, Montana must review its child support guidelines at least every four years. The Guidelines Review and Oversight Committee (GROC) conducts these reviews. The most recent review was completed in December 2024, with the next review scheduled for completion in December 2028.

The DPHHS updates the support tables annually to incorporate:

• Current U.S. federal poverty guidelines
• Updated IRS business mileage rates
• Economic data on child-rearing costs

Interested parties can participate in the review process by contacting guidelines@mt.gov.

More Montana Laws

• Montana Alimony Laws
• Montana Child Custody Laws
• Montana Divorce Laws

Frequently Asked Questions

What formula does Montana use to calculate child support?

Montana uses the Modified Melson Formula, not the Income Shares model. Montana adopted this three-stage approach in 1992 and is one of only three states (with Delaware and Hawaii) to use it. Stage 1 deducts a personal allowance for each parent ($20,748/year in 2026). Stage 2 applies a primary child support allowance from a published table ($6,224/year for one child in 2026). Stage 3 applies the Standard of Living Adjustment (SOLA), which takes a percentage of each parent's remaining income and shares it with the child. The SOLA rate is 14% for one child, rising to 47% for eight or more children.

How is child support calculated in Montana?

Montana calculates child support under ARM 37.62 using the Modified Melson Formula. Each parent's gross income is determined, then a personal allowance ($20,748/year in 2026) and allowable deductions are subtracted. Each parent's proportional share of the combined available income is calculated. From that, each parent contributes their share of the primary child support allowance plus any supplements for health insurance and child care. Any remaining income is then subject to the Standard of Living Adjustment (SOLA) to further share parental prosperity with the child. Parenting time adjustments apply when the non-custodial parent has more than 110 days of parenting time per year.

When does child support end in Montana?

Under MCA 40-4-208(5), child support in Montana ends when the child turns 18 or graduates from high school, whichever occurs later, but no later than the child's 19th birthday. Support may continue indefinitely if the child has a disability that causes financial dependence on the custodial parent.

How can I modify a child support order in Montana?

You can request a review of your child support order every 36 months without showing changed circumstances. To modify before 36 months, you must demonstrate a substantial change such as a 30% or greater change in income, a change in custody, or a significant increase in child care or medical expenses. Contact CSSD at (800) 346-5437 or your assigned investigator to begin the process.

What happens if I do not pay child support in Montana?

Montana enforces child support through wage withholding, tax refund interception, bank account seizure, property liens, credit bureau reporting, and license suspension. If arrears total six months of support, your driver's license, professional licenses, and recreational licenses can be suspended. Arrears over $2,500 can result in passport denial. The court can also hold you in contempt, with penalties of up to 5 days in jail, 120 hours of community service, and a $500 fine per violation.

Does Montana require health insurance as part of child support orders?

Yes. Under MCA 40-4-204, every child support order in Montana must include a medical support order. If a parent has health insurance available at a reasonable cost through their employer, they must add the child to that plan. Both parents may be required to share premiums, deductibles, and uninsured medical expenses based on their respective income percentages.