Montana uses the Modified Melson Formula per MCA §40-4-204. Three-step: self-support at 1.3× FPL, primary support, SOLA.
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Montana calculates child support using the Modified Melson Formula (one of only 3 states) established under MCA §40-4-204. This is a statutory formula that leaves limited room for judicial discretion on the base calculation amount, ensuring consistency and predictability for families across the state.
Melson: combined income after self-support × schedule × obligor share.
The calculation begins with determining each parent's net disposable income, which includes virtually all sources of income minus taxes, mandatory payroll deductions, and certain hardship deductions. The court then applies the statutory formula using the time each parent has primary physical responsibility for the children and the applicable income allocation brackets.
Beyond the base formula amount, Montanarequires additional contributions for mandatory add-on expenses. These typically include childcare costs necessary for the custodial parent's employment or education, uninsured healthcare expenses for the children, and in some cases, educational and travel costs. These add-ons are split between parents in proportion to their respective incomes.
Primary statute: MCA §40-4-204
Modified Melson Formula (one of only 3 states with Delaware and Hawaii).
Three-step: self-support, primary support, SOLA.
Approximate: 1 child ~17%, 2 ~25%, 3 ~30%, 4 ~34%, 5 ~37%.
Modified Melson Formula — unique to 3 states.
Self-support allowance at 1.3× FPL.
Answer a few questions about your income, custody, and children. Get your personalized estimate.
Residency Requirement
90-day residency (MCA §40-4-104)
Mandatory Waiting Period
No mandatory waiting period
No-Fault Ground
Irretrievably broken (MCA §40-4-104)
State Income Tax
Progressive ~2-6.75%.
Montana uses the Modified Melson Formula (one of only 3 states) under MCA §40-4-204. Montana uses the Modified Melson Formula per MCA §40-4-204. Three-step: self-support at 1.3× FPL, primary support, SOLA.
Key factors include both parents' income, the number of children, custodial time share, mandatory add-on expenses (childcare, health insurance), and any applicable deductions. Modified Melson Formula (one of only 3 states with Delaware and Hawaii).
Yes. Either parent can request a modification if there has been a material change in circumstances, such as a significant change in income, custody arrangements, or the needs of the child. The court will recalculate support using the same statutory formula.
Melson: combined income after self-support × schedule × obligor share.
Get a personalized child support calculation based on Montana's actual statutory formula.
Start My Free MontanaEstimate →This tool provides educational estimates based on Montana family law and does not constitute legal advice. Child support calculations are approximations of the statutory formula and may differ from court-ordered amounts. Consult a licensed Montana family law attorney before making decisions. Primary statute: MCA §40-4-204.