Child support in Montana
Montana uses a version of the Melson formula, which looks at both parents' incomes and the children's basic needs. To open a case, contact the Montana DPHHS Child Support Services Division (CSSD) at 1-800-346-5437.
Checked against official sources: Oct 25, 2026. · Free letters and checklist ↓
How much child support in Montana?
Montana uses its own version of the Melson formula. Each parent first keeps a personal allowance for basic needs (130% of the federal poverty level, $20,748 a year in the tables effective February 1, 2026). Then a basic amount for the children is shared by the parents in proportion to their income, and if a parent has income left over, a further share (standard of living adjustment) is added. Parenting days, child care and health costs also count.
Law: Mont. Code Ann. 40-4-204, 40-5-209; Admin. R. Mont. 37.62.101-148
We don't estimate Montana's amount here: its formula uses both parents' incomes and other facts, and a home-made number could mislead you. The official tool gives the real starting number:
Open a child support case in Montana
- Phone
- 1-800-346-5437
- Apply
- Apply online
- How to open a case
You can enroll with CSSD online, or mail the paper Enrollment Form with the $25 fee. CSSD can find the other parent, establish paternity, and set support through its own administrative notice process. Parents can agree, send new information, or ask for a hearing. You can also ask a District Court for support in a divorce or parenting plan case.
- Application fee
$25 non-refundable enrollment fee. No fee if you get Montana public assistance (Medicaid/Healthy Montana Kids, SNAP, cash assistance, child care grant, or Child and Family Services). Source: CSSD Enrollment Form, 'Cost of Services'.
- Forms
- Paternity (legal fatherhood)
Unmarried parents can sign the Voluntary Paternity Acknowledgment form (Office of Vital Records); the father's name then goes on the birth certificate. If paternity is disputed, CSSD can arrange genetic (DNA) testing when you receive child support services, or a court can decide. A husband is presumed the father of a child born during the marriage or within 300 days after it ends.
Montana child support by topic
How support is calculated in Montana
The model, the percentages or the official calculator, and low-income rules.
Change child support in Montana
When you can ask, how to ask, and a review letter.
Collect unpaid support in Montana
Collection tools, interest and license rules, and a letter.
When support ends in Montana
The end age, high school and disability rules.
How child support is figured in Montana
- Model
- Melson formula
- How it works
Montana uses its own version of the Melson formula. Each parent first keeps a personal allowance for basic needs (130% of the federal poverty level, $20,748 a year in the tables effective February 1, 2026). Then a basic amount for the children is shared by the parents in proportion to their income, and if a parent has income left over, a further share (standard of living adjustment) is added. Parenting days, child care and health costs also count.
- Low income
A minimum contribution is set in every case. If your income after deductions is at or below the personal allowance, the minimum is a small share of your income from a table (0% to 11%). If your income is above the personal allowance but the calculated support is under 12% of your income after deductions, the minimum is 12%.
Law: Admin. R. Mont. 37.62.126
- Official calculator
- Official Montana child support calculator
- Health insurance and medical costs
Every Montana support order must include medical support, usually health insurance. A parent who can get reasonable-cost employer health coverage may be required to provide it. If an order has no medical support, or medical support is violated, support can be modified right away.
Law: Mont. Code Ann. 40-4-208(2)(c), 40-5-804
Law: Mont. Code Ann. 40-4-204, 40-5-209; Admin. R. Mont. 37.62.101-148
Change a child support order in Montana
- When a change is allowed
Through CSSD: you can ask for a review once 36 months have passed since the order was entered or last reviewed. Sooner, you must show a significant change, such as a change in physical custody, child care or medical costs, number of children, or a parent's income changing by at least 30%. By law, a court can change support only if circumstances changed so much, and for so long, that the old terms are unconscionable, or if both parents agree in writing, or when CSSD asks in a case it handles. In general, an order cannot be changed within 12 months after it was set or last changed. If the order has no medical support, it can be changed right away. A change applies only to payments due after the other parent gets notice.
Law: Mont. Code Ann. 40-4-208(1)-(2)
- How to ask
Ask your CSSD case investigator for a Request for Review packet. CSSD recalculates support and sends a notice; parents can correct information, agree, or ask for an administrative hearing. The process usually takes up to 180 days. Or file a motion to modify in District Court.
Can I ask for a change? Check your situation
Collect unpaid child support in Montana
Arrears means support that is past due. The child support agency can use these tools to collect it:
- Collection tools
- Income withholding
- Federal and state tax refund offset
- Federal administrative payment offset
- Credit bureau reporting
- Passport denial
- Driver's, occupational and recreational (hunting/fishing) license suspension
- Lottery winnings intercept ($600 and over)
- Freezing and seizing bank accounts and other assets
- Liens on real and titled personal property
- License suspension
A notice of intent to suspend a license can be issued when past-due support equals 6 months of payments or more. The license is suspended 60 days after service unless the parent pays in full or agrees to a payment plan.
Law: Mont. Code Ann. 40-5-701(3), 40-5-702
- Contempt of court
You can ask the District Court to hold the other parent in contempt for not paying. The court self-help page has a 'Petition for Contempt of Court for Failure to Pay Support' packet.
- Interest on unpaid support
Montana judgment interest is the bank prime rate (set each January 1) plus 3%, not compounded. CSSD does not calculate interest; it collects interest on unpaid support only after the interest has been turned into a lump-sum judgment by an order.
Law: Mont. Code Ann. 25-9-205
Source: CSSD Enrollment Form, Terms and Conditions
Law: Mont. Code Ann. Title 40, ch. 5; 40-5-701 to 40-5-713
When child support ends in Montana
- Support ends
18, or graduation from high school if the child is still enrolled, whichever is later, but no later than the 19th birthday
- Exceptions
Support can continue past 19 for a child with a disability who is financially dependent on the custodial parent, when that parent is the primary caregiver. Parents can also extend support by written agreement or the decree can say so. Support does not end when the paying parent dies.
Law: Mont. Code Ann. 40-4-208(5)-(7)
Law: Mont. Code Ann. 40-4-208(5)-(6)
When does support end? Check your situation
Free help in Montana
- Montana Legal Services Association HelpLine and intake · 1-800-666-6899
- MontanaLawHelp.org: Child support
- Montana Court Help Program · (406) 841-2975
- Find free legal help at LawHelp.org
Official self-help
Free letters and checklist
Ask the agency to review (change) your order
A letter to the child support agency asking for a review and adjustment.
Ask the agency to collect unpaid support
A letter asking the agency to enforce the order and collect what is past due.
Checklist: what to bring to open a case
IDs, birth certificates, the other parent's details and your papers, with Montana's agency contact.
Good to know in Montana
- Montana is one of the few states using the Melson formula, which protects a personal allowance for each parent before support is figured (CSSD Guidelines History).
- CSSD updates the guideline tables every year for the new federal poverty level; the current tables took effect February 1, 2026 (CSSD Tables CS 404.2).
- A parent who owes past-due support can lose hunting and fishing licenses, not only a driver's license (CSSD Enforcement page).
Changes in 2024–2026
CSSD finished its 2024 quadrennial guidelines review (report dated December 27, 2024) and updates the guideline tables yearly; the tables now in use took effect February 1, 2026 (personal allowance $20,748; primary child support allowance $6,224 a year for one child). The next review is due December 2028.
Federal rules in every state
- Applying. If you don't get TANF, Medicaid or foster care help, a state may charge an application fee of up to $25 to open a child support case. Law: 42 U.S.C. 654(6)(B)(i)
- Yearly fee. If you never got TANF and the agency collected at least $550 for you in a year, the state charges a $35 yearly fee. It can come out of your support, but never out of the first $550. Law: 42 U.S.C. 654(6)(B)(ii)
- Review every 3 years. If your case is with the child support agency, either parent can ask it to review the order every 3 years and adjust it to the guidelines. Law: 42 U.S.C. 666(a)(10)(A); 45 CFR 303.8
- Past-due support. Each unpaid payment becomes a judgment on the day it is due. It can't be lowered later, except back to the date the other parent got notice of a request to change the order. Law: 42 U.S.C. 666(a)(9)
- Tax refunds. The federal government can take a federal tax refund to pay past-due child support. Law: 42 U.S.C. 664
- Passports. A parent who owes more than $2,500 in past-due support can be refused a passport. Law: 42 U.S.C. 652(k)
- Pay withholding limit. For support, up to 50% of take-home pay can be withheld if the parent supports another spouse or child, or 60% if not. It is 55% or 65% when support is more than 12 weeks behind. Law: 15 U.S.C. 1673(b)
- How long support lasts. How long support lasts follows the law of the state that made the order, even if you move. Law: 28 U.S.C. 1738B(h)(2)
Questions about child support in Montana
How is child support calculated in Montana?
Montana uses its own version of the Melson formula. Each parent first keeps a personal allowance for basic needs (130% of the federal poverty level, $20,748 a year in the tables effective February 1, 2026). Then a basic amount for the children is shared by the parents in proportion to their income, and if a parent has income left over, a further share (standard of living adjustment) is added. Parenting days, child care and health costs also count.
Is there an official child support calculator for Montana?
What if the paying parent has a low income in Montana?
A minimum contribution is set in every case. If your income after deductions is at or below the personal allowance, the minimum is a small share of your income from a table (0% to 11%). If your income is above the personal allowance but the calculated support is under 12% of your income after deductions, the minimum is 12%.
How do I apply for child support in Montana?
You can enroll with CSSD online, or mail the paper Enrollment Form with the $25 fee. CSSD can find the other parent, establish paternity, and set support through its own administrative notice process. Parents can agree, send new information, or ask for a hearing. You can also ask a District Court for support in a divorce or parenting plan case.
Does it cost money to open a child support case in Montana?
$25 non-refundable enrollment fee. No fee if you get Montana public assistance (Medicaid/Healthy Montana Kids, SNAP, cash assistance, child care grant, or Child and Family Services). Source: CSSD Enrollment Form, 'Cost of Services'.
When can child support be changed in Montana?
Through CSSD: you can ask for a review once 36 months have passed since the order was entered or last reviewed. Sooner, you must show a significant change, such as a change in physical custody, child care or medical costs, number of children, or a parent's income changing by at least 30%. By law, a court can change support only if circumstances changed so much, and for so long, that the old terms are unconscionable, or if both parents agree in writing, or when CSSD asks in a case it handles. In general, an order cannot be changed within 12 months after it was set or last changed. If the order has no medical support, it can be changed right away. A change applies only to payments due after the other parent gets notice.
How do I ask to change child support in Montana?
Ask your CSSD case investigator for a Request for Review packet. CSSD recalculates support and sends a notice; parents can correct information, agree, or ask for an administrative hearing. The process usually takes up to 180 days. Or file a motion to modify in District Court.
What happens if child support is not paid in Montana?
Arrears means support that is past due. The child support agency can use these tools to collect it: Income withholding; Federal and state tax refund offset; Federal administrative payment offset; Credit bureau reporting; Passport denial; Driver's, occupational and recreational (hunting/fishing) license suspension; Lottery winnings intercept ($600 and over); Freezing and seizing bank accounts and other assets; Liens on real and titled personal property.
Can a license be suspended for unpaid child support in Montana?
A notice of intent to suspend a license can be issued when past-due support equals 6 months of payments or more. The license is suspended 60 days after service unless the parent pays in full or agrees to a payment plan.
Can a parent be held in contempt for not paying in Montana?
You can ask the District Court to hold the other parent in contempt for not paying. The court self-help page has a 'Petition for Contempt of Court for Failure to Pay Support' packet.
Is there interest on unpaid child support in Montana?
Montana judgment interest is the bank prime rate (set each January 1) plus 3%, not compounded. CSSD does not calculate interest; it collects interest on unpaid support only after the interest has been turned into a lump-sum judgment by an order.
When does child support end in Montana?
18, or graduation from high school if the child is still enrolled, whichever is later, but no later than the 19th birthday
Does child support continue while my child finishes high school in Montana?
18, or graduation from high school if the child is still enrolled, whichever is later, but no later than the 19th birthday
Can child support continue past the usual age in Montana?
Support can continue past 19 for a child with a disability who is financially dependent on the custodial parent, when that parent is the primary caregiver. Parents can also extend support by written agreement or the decree can say so. Support does not end when the paying parent dies.
How is paternity established in Montana?
Unmarried parents can sign the Voluntary Paternity Acknowledgment form (Office of Vital Records); the father's name then goes on the birth certificate. If paternity is disputed, CSSD can arrange genetic (DNA) testing when you receive child support services, or a court can decide. A husband is presumed the father of a child born during the marriage or within 300 days after it ends.
Who pays for the child's health insurance in Montana?
Every Montana support order must include medical support, usually health insurance. A parent who can get reasonable-cost employer health coverage may be required to provide it. If an order has no medical support, or medical support is violated, support can be modified right away.
More help on our sister sites
Sources
- CSSD Montana Child Support Guidelines
- Montana Child Support Guidelines Tables, effective Feb. 1, 2026 (CS 404.2)
- Montana Child Support Guidelines - ARM 37.62.101-148
- CSSD Guidelines History
- CSSD Enrollment Form for Services
- CSSD Support Order Modification
- CSSD Enforcement of Support Orders
- CSSD Paternity Information
- Mont. Code Ann. 40-4-208
- Mont. Code Ann. 40-5-701
- Mont. Code Ann. 40-5-702
- Mont. Code Ann. 25-9-205
- Montana Courts: Child Support
- CSSD Guidelines Worksheets and Instructions
Last checked: Oct 25, 2026.
- State plan requirements: application fee, annual fee, safeguards, 42 U.S.C. 654
- Required state laws: arrears as judgments, review every 3 years, UIFSA, 42 U.S.C. 666
- Federal tax refund offset, 42 U.S.C. 664
- Passport denial for child support arrears, 42 U.S.C. 652(k)
- Garnishment limits for support orders, 15 U.S.C. 1673(b)
- Full faith and credit for child support orders, 28 U.S.C. 1738B
- Office of Child Support Enforcement (federal)