Child support · ID
Idaho child support calculator
Rule 120 of the Idaho Rules of Family Law Procedure has no lookup table: it works like a tax schedule run in reverse.
Rules read on official Idaho pages on · Checked by Radif Partners · How we calculate
- Model
- State formula
- Income counted
- Adjusted gross
- Shared parenting
- From 92 overnights
- 1 child, $5,000 / $3,000
- $639
- a month
Idaho does not publish a grid of incomes and amounts. Rule 120 of the Idaho Rules of Family Law Procedure applies a falling percentage to each slice of the parents' combined annual Guidelines Income, the way a tax schedule applies rates to slices of income. For one child the first $10,000 is taken at 18%, the next slice at 17%, and the rate keeps sliding to 5% above $150,000; for two children it starts at 26%. With $3,000 and $1,500 of gross monthly income and two children, the combined obligation is $1,023 a month and the higher earner owes $682. Parenting time enters through one number: once each parent has more than 25% of the overnights, the obligation is multiplied by 1.5 and offset, which takes this example to $636. The schedules stop at $440,000 of combined income a year.
Guideline child support in Idaho, per month
$639
$7,663 a year
| Combined Guidelines Income, a year | $96,000 |
| Basic child support from the bracket percentages, 1 child, a month | $1,022 |
| Paying parent’s share of Guidelines Income | 62.5% |
Estimate under the Idaho guideline as published, from the incomes you enter. Deviations, imputed income, other children and the judge's findings can change the order. How this is calculated.
Slices of income instead of rows
The Supreme Court of Idaho wrote its guideline as 11 brackets for each number of children, one to 5: 5 slices of $10,000, 5 of $20,000, then one of $290,000. Each slice has its own rate, and only the income inside the slice gets that rate. For two children the rates read 26%, 25%, 23%, 22%, 20%, 17%, 13%, 9%, 8%, 8%, 8%. The effect is that a family's average rate drifts down gently as income rises; there is no jump from one row to the next and no rounding to a table line. The rule prints a monthly figure for each slice, rounded to the dollar, which is why its own example adds up to a dollar more than the exact computation.
Our case works like this: $3,000 plus $1,500 is $54,000 a year. The first $50,000 pass through the first five slices, the rest through the sixth, and the total divided by 12 gives $1,023. The parent who earns two thirds of the income owes two thirds of it.
The 25% line on the calendar
Rule 120(i)(3) counts overnights in a calendar year. A schedule of alternate weekends, Friday to Sunday, stays well below the line, and that parent pays the full share. Shared physical custody begins when the child spends more than 25% of the overnights with each parent, 92 nights in our calculator. Then the obligation is multiplied by 1.5, each parent's part is weighted by the time the child spends with the other one, and the two amounts offset. At 91 nights our example stays at $682; at 92 it is $636; at 150 it is $393. The rule adds a guard: nobody pays more under shared custody than without it.
Small incomes, large incomes, five children
Rule 120 says support should rarely be zero. Below $800 of monthly income the court looks at living expenses, and the presumed minimum is $50 per child per month: a parent earning $400 with two children shows $104 in the calculator. At the other end, the brackets cover the first $440,000 of combined income a year; anything above is weighed against the child's needs, so we do not compute it. The schedules stop at 5 children. For a state that reads net income in a classic table, compare Nebraska.
The Idaho guideline this calculator applies
| Rule | Idaho |
|---|---|
| Model | Income shares computed with marginal percentage brackets of combined annual Guidelines Income |
| Income counted | Adjusted gross income: gross income minus the deductions the guideline allows. |
| Shared parenting | Cross-credit formula from 92 overnights a year, basic amount × 1.5 |
Monthly support for one paying parent, the other parent without income
| Paying parent’s monthly income | 1 child | 2 children | 3 children | 4 children |
|---|---|---|---|---|
| $2,000 | $342 | $502 | $582 | $642 |
| $3,000 | $487 | $727 | $847 | $937 |
| $4,000 | $620 | $933 | $1,093 | $1,213 |
| $5,000 | $742 | $1,108 | $1,300 | $1,442 |
| $6,000 | $857 | $1,272 | $1,493 | $1,655 |
| $8,000 | $1,022 | $1,512 | $1,793 | $1,995 |
| $10,000 | $1,133 | $1,683 | $2,025 | $2,267 |
| $12,500 | $1,258 | $1,883 | $2,300 | $2,592 |
| $15,000 | $1,383 | $2,083 | $2,575 | $2,917 |
| $20,000 | $1,633 | $2,483 | $3,125 | $3,567 |
How the amount is set. Basic child support = sum over brackets of (percentage x part of combined annual Guidelines Income in that bracket), for the number of children; the brackets are the first $10,000, then four further $10,000 bands, then five $20,000 bands, then the next $290,000 (up to $440,000). Monthly amount = annual / 12 (the rule prints each bracket's monthly amount rounded to the nearest dollar). Each parent owes the total in proportion to his or her share of combined Guidelines Income; with 25% or less of overnights the non-custodial parent pays his or her share (I.R.F.L.P. 120(i)(1), (i)(3)). Above $440,000 the court considers listed factors for additional support (120(i)(7)). The schedules do not limit support for more than five children (120(i)(2)). source
Income. Guidelines Income = each parent's gross income before taxes from any source (wages, commissions, bonuses, dividends, pensions, interest, Social Security, workers' compensation, unemployment, disability, alimony/maintenance received, veteran's benefits, education grants, etc.), plus significant employment benefits and potential income if voluntarily unemployed/underemployed; overtime or a voluntary second job may be excluded under stated conditions; business income = gross receipts minus ordinary and necessary expenses (straight-line depreciation, half of self-employment tax). Minus: other court-ordered child support or maintenance, maintenance ordered in the current case, regular support paid without order, and the Guidelines amount for other children living in the home (I.R.F.L.P. 120(e)-(f)).
Parenting time. If the child spends more than 25% of the overnights in a year with each parent, the basic obligation is multiplied by 1.5, then by each parent's income percentage, then by the percentage of time the child spends with the other parent; the obligations are offset and the parent owing more pays the difference; no parent pays more than if all children lived with the other parent (I.R.F.L.P. 120(i)(4)). With 25% or less of overnights, the court may reduce support (reasonable reduction 50%) during visits of 14 consecutive days or more (120(i)(5)). Split custody uses the 1.5 multiplier per 120(i)(6).
Child care and health care. Not in the basic amount; the court may order reasonable work-related child care shared in proportion to Guidelines Income, normally paid directly between parents (I.R.F.L.P. 120(g)(1)). Children's health insurance premiums and uncovered health care expenses are shared pro rata to Guidelines Income, paid directly or as a credit/addition to support; an expense over $500 per course of treatment must be approved in advance (120(g)(4)). The court also considers transportation costs (120(g)(2)), the allocation of the federal/Idaho child tax benefit using the official tax-benefit tables (120(g)(3)) and dependency benefits paid because of the payer's disability or retirement (120(g)(5)).
Low incomes. Rarely should support be zero. If the paying parent's monthly income is below $800.00, the court reviews incomes and living expenses to set the maximum support that does not deny the parent a minimum subsistence; there is a rebuttable presumption that minimum support is at least $50.00 per month per child (I.R.F.L.P. 120(c)(4)).
When support ends. The Guidelines apply to children under 18, or children pursuing high school education up to age 19; support for post-high-school education is not available under the Guidelines (I.R.F.L.P. 120(a)). source
Worth knowing in Idaho
- Idaho does not use a lookup table: support is the sum of marginal percentages applied to annual combined Guidelines Income, falling from 18% (one child) / 26% (two) on the first $10,000 to 5% / 8% above $150,000 (I.R.F.L.P. 120(i)(1)). source
- A parent is not deemed underemployed if working full time in the same or similar occupation for more than six months before filing or separation, and ordinarily not while caring for a child under 6 months (I.R.F.L.P. 120(e)(3)(A)). source
- Shared custody starts when each parent has more than 25% of the overnights; the obligation is then multiplied by 1.5 and cross-credited (I.R.F.L.P. 120(i)(4)). source
- The parent not receiving the child tax benefit is entitled to a pro rata share of it, computed from official tax-benefit tables, as a credit against or addition to support (I.R.F.L.P. 120(g)(3)). source
- Rule 120 was adopted July 1, 2021 and last amended June 3, 2025, effective July 1, 2025. source