Child Support Calculations in Arizona

Arizona uses the Income Shares model to calculate child support, governed by the Arizona Child Support Guidelines and A.R.S. §25-320. The Guidelines estimate what an intact household would spend on children at various income levels and allocate that amount between parents. Whether you're navigating an uncontested or contested divorce, understanding how Arizona calculates child support is essential.

The Income Shares Model

Arizona's Income Shares model determines the Basic Child Support Obligation (BCSO) from the Schedule of Basic Support Obligation based on Combined Adjusted Child Support Income (CACSI) and the number of children. The schedule provides values up to a maximum CACSI of $30,000/month.

Above the cap: If CACSI exceeds $30,000 and no party requests a higher amount, the court uses the $30,000-row amount. If a party requests more, the court may set a higher amount based on the child's needs, income disparity, and case-specific factors.

Determining Child Support Income

"Child Support Income" (CSI) includes income from nearly all sources before deductions:

• Wages, salaries, commissions, bonuses, and severance pay
• Self-employment income (gross minus ordinary expenses, plus half of self-employment tax)
• Dividends, interest, trust income, and capital gains
• Pensions, retirement, workers' comp, unemployment, and disability
• Military pay including BAH/BAS allowances
• Spousal maintenance received (maintenance paid is deducted)

Excluded: Means-tested benefits (TANF, SSI, food stamps), stepparent/new spouse income, and child support received from other relationships.

Imputation: If a parent is voluntarily unemployed or underemployed, the court may attribute income based on full-time work at minimum wage ($14.70/hour for 2025).

Parenting-Time Adjustments

Arizona uses a detailed parenting-time table that converts annual days with the lesser-time parent into a percentage credit applied to the BCSO:

• 0-19 days: 0% adjustment
• 20-34 days: 2.5%
• 35-49 days: 5%
• 50-69 days: 7.5%
• 70-84 days: 10%
• 85-99 days: 15%
• 100-114 days: 17.5%
• 115-129 days: 20%
• 130-142 days: 25%
• 143-152 days: 32.5%
• 153-163 days: 40%
• 164+ days: 50% (essentially equal time)

Counting days: 24 hours = 1 day; 12-23 hours = 1 day; 6-11 hours = ½ day; 3-5 hours = ¼ day. School/daycare time doesn't count for either parent.

Estimate Your Arizona Child Support

Use our calculator to get a preliminary estimate. For official calculations, use the Arizona Child Support Calculator.

Self-Support Reserve (SSR)

Arizona protects low-income obligors through the Self-Support Reserve test:

• SSR formula: 80% × (state minimum wage × 40 hours × 52 weeks ÷ 12 months)
• 2025 SSR: $2,038.40/month (with $14.70/hour minimum wage)
• Application: If paying support would reduce the obligor's income below the SSR, the order may be reduced
• Recipient consideration: Before reducing, courts consider the receiving parent's ability to self-support

Add-Ons and Adjustments

Beyond the BCSO, Arizona adds several expenses to create the Combined Child Support Obligation (CCSO):

• Older-child adjustment: Add 10% to the BCSO portion for each child age 12 or older
• Health insurance: Child's allocable share of medical, dental, and vision premiums
• Work-related childcare: Actual costs necessary for work or job search (annualized)
• Education expenses: Reasonable private/special school tuition if agreed or ordered
• Extraordinary expenses: Costs for gifted or special-needs children

Common Calculation Mistakes

• Miscounting parenting days: Use the 24/12/6/3-hour blocks; school time doesn't count
• Forgetting the older-child add-on: Children 12+ get a 10% increase to their BCSO portion
• Ignoring the $8 clearinghouse fee rule: If calculated support is below $8, no order is entered (not a deviation)
• Using outdated SSR: The SSR changes with minimum wage; 2025 rate is $2,038.40/month
• Equal time ≠ zero support: Even with 50/50 custody, the higher earner typically pays some support

Modification and Duration

Arizona provides pathways to modify support:

• Substantial change: Any party may seek modification upon substantial and continuing change
• 15% simplified procedure: If recalculation differs by 15% or more from the current order, that variance is evidence of substantial change
• Effective date: Generally the first day of the month after notice of the petition

Duration: Support ends at age 18, or while actually attending high school (or equivalency program) but not beyond age 19. Support may continue for severely disabled adult children if the disability began before majority.

Enforcement and Interest

Arizona provides robust enforcement tools:

• 10% simple interest: Accrues on arrears from the end of the month after the month due
• Income withholding: Employers must begin withholding within 14 days; up to 50% of disposable earnings
• License suspension: Driver's, professional, and recreational licenses after 6 months' arrears
• Federal offsets: Tax refund intercepts ($500+ arrears); passport denial ($2,500+ arrears)

Key Takeaways

• Income Shares model: BCSO from schedule, allocated by income shares
• $30,000/month cap: Above this, court discretion applies with findings
• Detailed parenting-time table: 0% to 50% credit based on days (164+ = equal time)
• 10% older-child add-on: For children age 12 or older
• SSR protection: $2,038.40/month (2025) ensures obligor retains basic income
• 10% simple interest: Accrues on unpaid support

For more information about Arizona divorce processes, see our Arizona divorce timeline and filing checklist.