What is the income shares model used in Arizona?

Arizona uses the income shares model under A.R.S. § 25-320, which is based on the principle that children should receive the same proportion of parental income they would have received if the parents lived together. The model combines both parents' incomes, determines the total child-rearing cost at that income level (from economic data tables), and allocates the cost between parents based on their proportional income share. Arizona adopted this model in 2005, replacing the older percentage-of-income model.

How is adjusted gross income calculated in Arizona?

Adjusted Gross Income (AGI) in Arizona is gross income from all sources, minus only court-ordered child support or spousal maintenance paid for other children or former spouses. Gross income includes: wages, salaries, commissions, bonuses, tips, self-employment income, rental income, interest and dividends, retirement distributions, unemployment benefits, workers' compensation, disability payments, and any other income. Taxes, FICA, retirement contributions, and other voluntary deductions are NOT subtracted. If income is variable, the court may average income over 1-2 years or use a representative month.

What is the shared parenting adjustment in Arizona?

Arizona law provides a shared parenting adjustment under A.R.S. § 25-320(G) when the non-custodial parent has parenting time of at least 146 overnights per year (approximately 40% or more). The adjustment reduces the basic child support obligation to account for the non-custodial parent's direct expenditures during parenting time. The formula is: Adjusted CSO = Basic CSO × [1 - (1.5 × NCP parenting time percentage × NCP income percentage)]. This formula recognizes that both parents incur direct costs for the child during their respective parenting time.

How does Arizona handle high-income cases above $20,000/month?

The Arizona Child Support Guidelines Schedule caps combined adjusted gross income at $20,000/month. For cases above this threshold, courts have two options: (1) Extrapolation: Apply the marginal percentage from the highest income level in the schedule to the excess income, or (2) Actual Expenses: Consider the actual reasonable needs of the children, taking into account the family's standard of living, the children's demonstrated needs, and evidence of typical expenditures. Courts may also deviate from guidelines if the standard calculation would be unjust or inappropriate in high-income cases.

What additional expenses are added to basic child support in Arizona?

Beyond the basic child support obligation, Arizona courts add prorated shares of: (1) Childcare costs: Work-related or education-related childcare expenses, allocated by income share; (2) Health insurance premiums: Cost of adding children to a parent's health insurance policy, allocated by income share; (3) Unreimbursed medical expenses: Typically extraordinary medical, dental, vision, or mental health expenses not covered by insurance (often split 50/50 or by income share); (4) Educational expenses: Private school tuition or special education costs (if agreed or ordered); (5) Extracurricular activities: Costs for sports, music, camps, etc. (if agreed or court-ordered). Each additional expense is allocated based on the parents' proportional income shares unless the court orders a different allocation.

Can Arizona courts deviate from the child support guidelines?

Yes. Arizona courts may deviate from the guideline amount if applying the guidelines would be "inappropriate or unjust" under A.R.S. § 25-320(D). Deviation factors include: (1) financial resources and needs of the children and parents; (2) standard of living the child would have enjoyed if the marriage had not been dissolved; (3) physical/emotional condition and educational needs of the child; (4) child's financial resources and earning ability of the parents; (5) excessive or unusual expenses incurred by either parent; (6) income from property; (7) fringe benefits; (8) any other relevant factor. If the court deviates, it must make written findings explaining why the guideline amount is inappropriate and how the deviation serves the child's best interest.

How is self-employment income calculated for Arizona child support?

Self-employment income is gross receipts minus ordinary and necessary business expenses. However, Arizona courts scrutinize deductions to prevent income manipulation. Disallowed deductions include: excessive or personal expenses (meals, travel unrelated to business, personal vehicle use), depreciation on assets also used personally, and discretionary retirement contributions. The court may average self-employment income over 1-2 years if income fluctuates. If a self-employed parent underreports income or operates their business at a loss to avoid support, the court may impute income based on earning capacity, prior income history, or industry standards.

What is the self-support reserve in Arizona child support?

Arizona's self-support reserve is $1,405/month (as of 2022), which is approximately equivalent to the federal poverty guideline for one person. This reserve protects low-income obligors from support orders that would leave them unable to meet their own basic needs. If the obligor's adjusted gross income minus the basic support obligation falls below the self-support reserve, the court may reduce the support amount using a low-income adjustment formula. The goal is to ensure the obligor retains enough income for housing, food, and basic necessities, while still providing some support for the child. The self-support reserve is adjusted periodically to reflect cost-of-living changes.

Arizona Child Support Formula

Complete guide to Arizona's income shares child support model: calculation steps, deviation factors, shared parenting adjustments, and high-income cases

A.R.S. § 25-320Income Shares ModelUpdated 2025

Quick Facts

Formula Type

Standard

Income Shares Model

Considers both parents' incomes

A.R.S. § 25-320

Income Definition

Adjusted Gross Income

Before-tax income with adjustments

Arizona Child Support Guidelines

Schedule Maximum

Critical

$20,000/month

Combined income cap

Arizona Child Support Guidelines

Shared Parenting Threshold

146+ nights per year

Triggers adjustment formula

A.R.S. § 25-320(G)

Self-Support Reserve

Low-Income

$1,405/month

Protected minimum for obligor

Arizona Child Support Guidelines

Guideline Updates

Every 4 Years

Last updated 2022

Arizona Judicial Council

Overview of the Arizona Formula

Arizona uses the income shares model for child support calculations under A.R.S. § 25-320. This model is grounded in economic research showing that children should receive the same proportion of parental income they would have received in an intact household. Arizona adopted the income shares model in 2005, replacing the older percentage-of-income approach.

The formula considers both parents' incomes and uses a guideline schedule (developed from USDA expenditure data) to determine the basic child support obligation. The obligor (non-custodial parent) pays their proportional share to the obligee (custodial parent). Additional expenses—such as childcare, health insurance, and medical costs—are allocated separately based on each parent's income share.

Arizona's guidelines apply to combined adjusted gross incomes up to $20,000/month. For higher incomes, courts extrapolate or consider actual child expenses. The formula also includes a shared parenting adjustment for cases where the non-custodial parent has 146 or more overnights per year (approximately 40% parenting time).

Step-by-Step Calculation Process

Step 1: Determine Adjusted Gross Income

Calculate each parent's monthly adjusted gross income from all sources

Start with gross income from all sources: wages, self-employment, bonuses, commissions, rental income, interest/dividends, retirement income, unemployment, workers' compensation, and any other income. Subtract only court-ordered child support or spousal maintenance paid for other children/relationships. Do not subtract taxes or other expenses at this stage.

Step 2: Combine Adjusted Gross Incomes

Add both parents' adjusted gross incomes together

Combined Adjusted Gross Income (CAGI) = Parent A AGI + Parent B AGI. This combined figure is used to look up the Basic Child Support Obligation in the Arizona Child Support Guidelines Schedule. If CAGI exceeds $20,000/month, extrapolation rules apply.

Step 3: Determine Basic Child Support Obligation

Look up the Basic CSO from the Arizona schedule

Using the CAGI and number of children, find the Basic Child Support Obligation in the Arizona Child Support Guidelines Schedule. For incomes above $20,000/month, the court extrapolates using marginal percentages or considers actual expenses. The Basic CSO represents the estimated cost of raising children in an intact household at that income level.

Step 4: Apportion Pro-Rata by Income Share

Allocate the Basic CSO based on each parent's income percentage

Calculate each parent's percentage of CAGI: (Parent AGI ÷ CAGI) × 100. Multiply the Basic CSO by the non-custodial parent's percentage to get their initial support obligation. This reflects the principle that each parent should contribute to child support in proportion to their financial capacity.

Step 5: Add Adjustments and Additional Expenses

Adjust for shared parenting, childcare, health insurance, and other costs

Apply the shared parenting adjustment if the non-custodial parent has 146+ overnights per year (reduces support obligation). Add prorated shares of: childcare costs necessary for work/education, health insurance premiums for the children, and extraordinary expenses (private school, special needs, extracurricular). Subtract any low-income adjustment if applicable.

Key Components Explained

Frequently Asked Questions

Calculate Your Arizona Child Support

Use our interactive calculator to estimate your child support obligation or entitlement based on Arizona's income shares formula and current guidelines.

Go to Calculator

Related Arizona Resources

Deviation Factors

When and why courts deviate from guidelines

Modification Guide

How to change an existing order

Legal References & Content Accuracy

Legal References

statuteA.R.S. § 25-320 – Child support calculation (Arizona Revised Statutes)
officialArizona Child Support Guidelines – Official guideline schedule and worksheets
officialArizona DES Child Support Services – State enforcement agency resources

Content Accuracy & Updates

This guide is based on Arizona Revised Statutes and Child Support Guidelines in effect as of January 2025. Arizona child support laws are subject to legislative amendments and judicial interpretation.

This content is for educational purposes only and does not constitute legal advice. Every child support case is unique, and outcomes depend on individual facts, income evidence, and judicial discretion. For advice on your specific situation, consult a licensed Arizona family law attorney.

Last Updated: January 15, 2025
Content Review: Based on current Arizona statutes and guidelines

Arizona Child Support Formula

Quick Facts

Overview of the Arizona Formula

Step-by-Step Calculation Process

Key Components Explained

What Counts as Income?

How Does Shared Parenting Adjustment Work?

What Additional Expenses Are Included?

When Can Courts Deviate from Guidelines?

Frequently Asked Questions

What is the income shares model used in Arizona?

How is adjusted gross income calculated in Arizona?

What is the shared parenting adjustment in Arizona?

How does Arizona handle high-income cases above $20,000/month?

What additional expenses are added to basic child support in Arizona?

Can Arizona courts deviate from the child support guidelines?

How is self-employment income calculated for Arizona child support?

What is the self-support reserve in Arizona child support?

Calculate Your Arizona Child Support

Related Arizona Resources

Legal References & Content Accuracy

Legal References

Content Accuracy & Updates