Idaho Child Support Calculator

Idaho uses the Income Shares model. Idaho applies the Income Shares model under IRFLP 120 (amended June 2025, effective July 1, 2025). When each parent has the child more than 25% of overnights (92+ per year), the guideline obligation is multiplied by 1.5 before being divided proportionally between the parents.

Idaho's guideline runs on gross. That distinction matters: entering gross income into a formula built on net income (or the reverse) produces a materially wrong figure. Most states count income from essentially any regular source -- wages, self-employment, bonuses, commissions, rental and investment income, and many benefits -- not just salary.

Not necessarily. In Idaho: when each parent has the child more than 25% of overnights (92+ per year), the guideline obligation is multiplied by 1.5 before being divided proportionally between the parents. Because the guideline also weighs each parent's share of income, a significantly higher earner can still owe support at an even time split.

Yes. The figure produced by Idaho's Income Shares guideline is presumptive, not mandatory: a court can order a different amount when applying the guideline would be unjust or inappropriate for the specific case, and generally must state its reason on the record. Common grounds include extraordinary medical or educational expenses, a child's special needs, or costs the formula does not capture.

You have to file for a modification -- a change in your circumstances does not change what you owe on its own. Idaho, like most states, requires a substantial change in circumstances: a significant involuntary income change, a change in the parenting schedule, or a material change in the child's needs. Until a court or the state child support agency issues a new order, the existing amount stays fully enforceable and arrears keep accruing, and a modification is generally not applied retroactively before the date you filed -- so filing promptly matters. In Idaho, modifications are handled through Idaho Child Support Services for Families.