CoreParent™

Idaho child support: Rule 120's income brackets, shared custody, and a worked example

Idaho does not print a long lookup table. Rule 120 of the Idaho Rules of Family Law Procedure charges a falling percentage on each slice of the parents' combined yearly income, a bit like tax brackets, and then divides the result between the parents by income.

Estimate free

At a glance

ModelIncome shares on combined Guidelines Income (gross income before taxes), I.R.F.L.P. 120
ScheduleBracket percentages on yearly combined income: for two children, 26% of the first $10,000, falling to 8% at the top
High incomeBrackets cover combined income up to $440,000 a year; the court may add more above that
Shared custodyMore than 25% of the year's overnights with each parent: 1.5 multiplier, each share times the other parent's time, offset
MinimumRebuttable presumption of at least $50 per child per month
Support endsAge 18; the court may continue it while the child is in high school, up to age 19
AgencyChild Support Services, Idaho Department of Health and Welfare

How Idaho calculates child support

The Idaho Supreme Court writes the guidelines as Rule 120, and Idaho Code 32-706 makes the result presumptively correct unless a judge finds on the record that it would be unjust or inappropriate. Each parent's Guidelines Income starts with gross income from any source, including wages, bonuses, self-employment profit, Social Security, unemployment and alimony received, plus job perks such as a company car or free housing when they cut personal living costs.

Several things come off gross income first: support or spousal maintenance ordered in another case, maintenance ordered in the current case, support paid without an order where there is a pattern of payment, and, for a child of another relationship living in the parent's home, the guideline amount for that child on the parent's income alone. Overtime or a voluntary part-time second job can be left out for a parent who already works full time, if the court finds the conditions in the rule are met.

The two incomes are added and run through the bracket schedule for the number of children. The rule lists each bracket both as a percentage and as a monthly dollar figure, rounded to the dollar, so the basic obligation is the sum of the brackets the combined income reaches. That total is split in proportion to each parent's Guidelines Income on Form 6 (the standard worksheet) or Form 7 (shared, split or mixed custody).

Worked example: Idaho

  1. Parent A earns $5,000 a month in Guidelines Income and Parent B earns $2,500, so the parents have $7,500 a month together, which is $90,000 a year.
  2. For two children, Rule 120 charges 26% of the first $10,000 a year ($217 a month), 25% of the next $10,000 ($208), 23% ($192), 22% ($183), 20% ($167), then 17% of the next $20,000 ($283) and 13% of the next $20,000 ($217). The brackets reached add up to a basic obligation of $1,467 a month.
  3. Parent A has 66.7% of the combined income, so Parent A's part of the obligation is $978 and Parent B's part is $489.
  4. If Parent A has the children 25% of the overnights or fewer, Parent A pays $978 a month, about $11,736 a year, plus a share of insurance, uncovered health costs and any work-related child care the court orders.

This is an estimate, not legal advice. Figures are rounded to the dollar and leave out the insurance, childcare, and other adjustments your case may have. Try your own numbers in CoreParent's calculator, then confirm with the state's official calculator.

Shared physical custody in Idaho: the 25% line

Time is counted in overnights over a calendar year. Rule 120 gives its own example: every other weekend, Friday to Sunday, is 52 overnights, about 14% of the year, and that parent pays the plain schedule share. Once the children spend more than 25% of the year's overnights with each parent, which takes at least 92, the rule recognizes that two homes cost more and switches formulas.

The basic obligation is multiplied by 1.5, each parent takes an income share of that figure, and each share is multiplied by the percentage of time the children spend with the other parent. The two amounts are offset, and no parent pays more than under sole custody. With 120 overnights for Parent A and 245 for Parent B, the example drops from $978 to about $744 a month. At equal time Parent A still pays about $367, and a parent with more than half the overnights who ends up paying may ask the court to find the amount inappropriate.

Two other time rules are specific to Idaho. When a parent with 25% or fewer overnights has the children for 14 consecutive days or more, the court may reduce support during that stretch, and the rule calls 50% a reasonable reduction. In split custody, where each parent has at least one child, support is figured for each parent and offset.

Health insurance, uncovered care and child care

Every order must address health insurance, ideally from the parent who can get suitable employer coverage at the lower cost. Premiums and the children's uncovered health costs, including orthodontic, optical, dental, psychological and prescription costs, are shared by income percentage on top of basic support. Before a course of treatment that would leave the other parent more than $500 out of pocket, both parents must approve it in writing or a court order must allow it.

Basic support does not include work-related child care. The court may divide reasonable child care costs by income, usually paid directly between the parents. Because the child tax credit has value, the rule also has the court consider who claims the children and give the other parent a proportional share of that tax benefit.

Low income and the $50 floor

Rule 120 says support should rarely be zero. When the paying parent's monthly income is under $800, the court looks closely at both incomes and living expenses to set the most that can be paid without denying that parent minimum subsistence. There is a rebuttable presumption of at least $50 a month per child. Incarceration is not treated as voluntary unemployment.

When support ends

Idaho Code 32-706 sets support until age 18. If the child is still in high school after turning 18, the court may continue support until the child leaves high school or turns 19, whichever comes first. The guidelines do not cover college costs. When one of several children ages out, the order moves to the schedule amount for the remaining children rather than dropping by a simple fraction.

Changing an order

Under Idaho Code 32-709 a support order can be modified only on a substantial and material change of circumstances, and only for payments that come due after the motion is filed. A change in the guideline amount may itself qualify. In an agency case, Child Support Services generally reviews an order after three years at either parent's request, or sooner if a substantial change has lasted at least six months.

Collection and enforcement

Child Support Services, part of the Idaho Department of Health and Welfare, calculates proposed orders under the guidelines and files them with the court, which sets the final amount. Most Idaho orders include income withholding. The agency also intercepts tax refunds and lottery winnings, reports to credit bureaus, suspends licenses, files liens and can deny passports.

Documents you will need

Idaho child support FAQ

What percentage of income is child support in Idaho?

It depends on combined income. For two children Rule 120 charges 26% of the first $10,000 of the parents' combined yearly income, and the rate steps down by bracket to 8% at the top. The total is then split by each parent's share of income.

How much is child support for 2 kids in Idaho?

At $7,500 of combined monthly Guidelines Income the schedule gives $1,467 for two children. A parent earning 66.7% of that income with 25% of the overnights or fewer pays $978 a month before insurance, medical and child care shares.

Does 50/50 custody mean no child support in Idaho?

Not when incomes differ. The shared custody formula still leaves the higher earner owing the difference. In our example, where Parent A earns twice what Parent B does, equal time leaves about $367 a month.

Does Idaho child support continue after 18?

Only while the child is still in high school, and only if the court orders it: support can continue until the child finishes or leaves high school or turns 19, whichever is sooner. The guidelines provide no support for college.

Does overtime count as income for Idaho child support?

Usually it counts, but Rule 120 lets the court exclude overtime or a voluntary part-time second job for a parent who already works full time at least 48 weeks a year, when overtime is not a condition of the job and the parent did not change jobs to affect support.

Next steps

Sources

Verified against these official sources in October 2026:

Child support in every other state

All states

This is general educational information, not legal advice, and official figures change. Last verified: October 2026. Consult a licensed family-law attorney in Idaho.