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Child Support in Montana

Free calculator, modification rules, arrears interest, and 50/50 custody guide for Montana — 2026.

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Child Support Calculator
Estimate payments using Montana's Melson Formula
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Modification Checker
Does your income change qualify?
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Arrears Calculator
Past-due support with 10% interest
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50/50 Custody Guide
Does equal custody eliminate support?

Montana Child Support Facts — 2026

Formula modelMelson Formula
Income basisBoth parents' income
Support ends at age18
Modification threshold10% income change
Arrears interest rate10% per year
Official agencyMontana Child Support Agency ↗
Montana uses the Melson Formula. Considers each parent's self-support reserve before calculating child support.

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