How it works · official guideline
How child support is calculated in Idaho
Idaho combines both parents' gross Guidelines Income, applies declining percentage rates to successive slices of that combined income for the number of children, and divides the result between the parents in proportion to their incomes. Shared custody (each parent over 25% of overnights) uses a 1.5 multiplier and an offset.[1]
Key facts: child support in Idaho
| Guideline model | Income shares[1] |
|---|---|
| Percentages | 1 child: 18% of first $10,000 combined, 17% next $10,000, 15%, 14%, 13% … down to 5%; 2 children start at 26%[1] |
| Income counted | Gross income before taxes, less listed adjustments[1] |
| Shared parenting time | More than 25% of overnights with each parent: basic obligation × 1.5, cross-multiplied and offset[1] |
| Guideline last checked | October 26, 2026 |
Idaho’s model
Income shares
Income shares using published marginal percentage brackets on combined annual Guidelines Income (gross), split in proportion to each parent’s income.
No official calculator confirmed yet
Read the guideline: Idaho Rules of Family Law Procedure, Rule 120, Idaho Child Support GuidelinesThe state child support agency or your court clerk can run the official numbers.
Why no calculator here? We publish a calculator only after it reproduces the state’s official numbers exactly. We haven’t matched Idaho’s yet.
From the official text
The rules behind Idaho’s numbers
The guideline is Idaho Rules of Family Law Procedure, Rule 120, Idaho Child Support Guidelines. Open each rule to read the exact words.
- Percentages
1 child: 18% of first $10,000 combined, 17% next $10,000, 15%, 14%, 13% … down to 5%; 2 children start at 26%
Rates fall as combined income rises: for one child 18% of the first $10,000 of combined annual Guidelines Income, then 17%, 15%, 14%, 13% on the next $10,000 slices, 12% and 9% and 6% on $20,000 slices, and 5% above that; two children start at 26%, three at 30%, four at 33%, five at 36%.[1]
Official text · I.R.F.L.P. 120(i)(1)
“18% of the first $10,000 of combined Guidelines Income”
- Income counted
Gross income before taxes, less listed adjustments
Guidelines Income is each parent’s gross income before taxes (plus employment benefits or potential income where applicable), minus adjustments such as other support orders and spousal maintenance.[1]
Official text · I.R.F.L.P. 120(e)
“For purposes of these Guidelines, Guidelines Income will include the gross income (before taxes) of the parents and if applicable, employment benefits and/or potential income; less adjustments as set forth in subsection (f) of this rule.”
- Shared parenting time
More than 25% of overnights with each parent: basic obligation × 1.5, cross-multiplied and offset
When the child spends more than 25% of overnights with each parent, the basic obligation is multiplied by 1.5, split by income share, multiplied by the other parent’s time share, and offset; no parent pays more than without shared custody.[1]
Official text · I.R.F.L.P. 120(i)(4)
“If the child spends more than 25% of the overnights in a year with each parent, an adjustment in the Guidelines amount will be made.”
- Top of the guidelines
Schedules cover combined Guidelines Income up to $440,000/year
Support on the first $440,000 of combined income follows the schedules; above that the court may add support after considering relevant factors.[1]
Official text · I.R.F.L.P. 120(i)(7)
“The Guideline Income schedules are not a limitation on the award of child support for combined Guidelines Income above $440,000 per year.”
- Minimum order
Presumptive minimum $50 per month per child
Support should rarely be zero; a minimum of $50 a month per child is presumed, and payer incomes under $800 a month call for careful review.[1]
Official text · I.R.F.L.P. 120(c)(4)
“There is a rebuttable presumption that a minimum amount of support is at least $50.00 per month per child.”
Guideline: Idaho Rules of Family Law Procedure, Rule 120, Idaho Child Support Guidelines (Idaho Supreme Court; amended June 3, 2025, eff. July 1, 2025), checked October 26, 2026.
Estimate and general information only — not legal advice. MediationList is a directory, not a law firm, and doesn’t endorse any mediator. Guidelines change; confirm with the state child support agency or your court (sources checked October 26, 2026). See also divorce laws in Idaho and child support in every state.
Sources
Idaho’s child support guideline, rules and official tools, read on the official sites, with the date we checked each.