IDAHO SUPPORT GUIDELINE
Idaho child support calculator & worksheet
Idaho Rule of Family Law Procedure 120 uses both parents’ annual Guidelines Income and child-count marginal rates, with a different path once parenting time crosses the shared-custody threshold.
Current module status
| State | Idaho |
|---|---|
| Status | Active base worksheet module |
| Guideline model | income shares annual tranche |
| Primary income field | Combined annual Guidelines Income |
How Idaho child support law works
Legal starting point. Idaho Rule of Family Law Procedure 120 sets the child-support guideline. It uses both parents’ annual Guidelines Income and applies child-count marginal rates, with different treatment when parenting time passes the rule’s shared-custody threshold. Read Idaho Rules of Family Law Procedure, Rule 120.
How the guideline is calculated
The ordinary calculation determines a combined basic obligation and allocates it by the parents’ income shares. More than 25 percent overnights, split custody, tax benefits, health costs, transportation, other-child deductions, and deviations belong on the full Idaho worksheet.
What this site’s worksheet covers
Uses Idaho Rules of Family Law Procedure Rule 120, amended June 3, 2025 and effective July 1, 2025. Rule 120 bases the standard calculation on both parents’ annual Guidelines Income and applies marginal percentage rates by child count; the basic monthly obligation is divided between parents by Guidelines Income share. This module implements the ordinary primary-parenting-time base calculation where the paying parent has 25% or less of annual overnights. Shared physical custody over 25% overnights, split custody, tax-benefit adjustments, health insurance, child care, transportation, disability/retirement dependency benefits, other-child deductions and deviations require the full Idaho worksheet. For combined Guidelines Income above $440,000 per year, support on the first $440,000 is calculated under Rule 120 and any additional support is court-specific.
Documents that make the worksheet more useful
Affidavit Verifying Income and applicable Idaho Child Support Worksheet. Gather the records that support the income, parenting-time, insurance, child-care, and other adjustment entries that apply to the family. The calculator applies the guideline formula described above and identifies any listed worksheet line it does not compute.
For a filing or agreement, complete the official court forms linked on this page. They use the same guideline structure explained here, and the court applies it to the facts of the case.
Before you enter your numbers
Is Idaho shared custody determined by its label?
The support rule uses the actual overnight arrangement, not just a custody label. When each parent has the children for more than 25 percent of the overnights, the shared-custody calculation becomes relevant. The rule also distinguishes split and mixed arrangements when siblings do not follow one schedule.
Prepare this: Complete the income affidavit and count overnights for each child. Choose the standard worksheet or the shared, split, or mixed worksheet using those facts.
Read the relevant official instructions: Idaho Rules of Family Law Procedure, Rule 120.
These preparation notes explain one part of the state guideline. A new estimate does not change an existing order; a modification request does.
How Idaho cases actually get to a number
Determine Guidelines Income, compute a combined basic obligation with the child-count rates, then allocate by income share. Crossing more than 25 percent overnights is a structural change, not a small credit.
Idaho Rule of Family Law Procedure 120 uses both parents’ annual Guidelines Income and child-count marginal rates, with a different path once parenting time crosses the shared-custody threshold. That is a different path from neighboring states that use another model, so do not import a table, percentage, or overnight credit from somewhere else.
Parenting time in Idaho
The 25 percent overnight threshold is the Idaho fork. Below it, the ordinary calculation applies. Above it, shared-custody treatment applies. Count overnights the way the rule counts them.
Costs Idaho usually treats separately
- Health-care costs for the children
- Work-related child care
- Transportation between homes
- Tax-benefit adjustments the rule addresses
When Idaho courts leave the guideline
The guideline is rebuttable. Other-child deductions, imputed income, and extraordinary travel are typical deviation or adjustment facts. Do not hide them in Guidelines Income.
Official Idaho forms to keep beside this guide
Affidavit Verifying Income and applicable Idaho Child Support Worksheet. The calculator applies the guideline formula described above and identifies any listed worksheet line it does not compute. The primary authority is the published Idaho source. Fill the official form from source documents. Use this page only to check that you chose the right Idaho path—primary versus shared, table versus percentage, add-ons versus basic support.
Where this is typically filed
Magistrate division of the district court hears most family cases. Use the current Idaho Child Support Guidelines issued with I.R.F.L.P. 120.
Questions specific to Idaho
Is Idaho a percentage-of-payer state?
No. It uses combined Guidelines Income and marginal child-count rates, then allocates by share.
What does 25 percent of overnights do?
It can switch the case into shared-custody treatment. That is more than a rounding difference.
Are tax exemptions part of the guideline?
Tax benefits are addressed in the rule. Do not ignore them or double-count them in income.
Run the calculator
Open the free support calculator, select Idaho, complete the state worksheet, and print or export the output for review.