Arizona Child Support Calculator: How Support Is Calculated

Arizona uses the Income Shares Model to calculate child support. The idea is straightforward: determine what both parents would have spent on the child if they still lived together, then split that amount proportionally based on each parent's income. The overnight count — how many nights the child spends with each parent — adjusts the final number.

The state provides a free online calculator through the ezCourtForms system, but the calculator only works if you feed it accurate inputs. Understanding what goes into each field prevents expensive errors.

Step 1: Calculate Each Parent's Gross Income

"Child support income" in Arizona means gross monthly income before taxes or deductions. This includes:

• Wages, salaries, and bonuses
• Self-employment income (gross receipts minus ordinary business expenses)
• Commissions and tips
• Unemployment and workers' compensation benefits
• Social Security and disability payments
• Rental income
• Interest and dividends
• Cash value of in-kind employment benefits (company car, housing allowance)

If a parent is voluntarily unemployed or underemployed, the court can impute income — attribute earning capacity based on work history, education, and the local job market. A parent who quits a $75,000 job to work part-time at $25,000 without a legitimate reason will be treated as if they still earn $75,000.

Step 2: Find the Basic Support Obligation

Once both parents' gross monthly incomes are added together, the court references Arizona's Schedule of Basic Support Obligations — a lookup table published by the Arizona Supreme Court. The table maps combined income and number of children to a base support amount.

The schedule caps at $30,000/month combined income. Above that threshold, the court uses the best-interests standard to determine whether additional support is warranted.

Older child adjustment: If a child is 12 or older, their share of the basic support obligation increases by 10%. Teenagers cost more — food, clothing, activities, and transportation all scale up.

Step 3: Add Adjustments

The total child support obligation includes four categories of additional costs beyond the basic obligation:

• Health insurance premiums — Only the children's portion of the premium, not the parent's individual coverage
• Work-related childcare — Daycare, after-school care, and summer programs needed so both parents can work
• Education costs — Private school tuition, if applicable and agreed upon or ordered by the court
• Extraordinary expenses — Special medical or developmental needs not covered by insurance

Each parent pays their proportionate share of these costs based on income. If Parent A earns 60% of the combined income, they cover 60% of these adjustments.

Step 4: Apply the Overnight Adjustment

This is where the parenting time schedule directly affects the dollar amount. Arizona's guidelines use the number of overnights each parent has per year to adjust the basic support obligation.

The logic: a parent who has the child more nights per year already bears more of the direct costs (food, utilities, transportation). The overnight adjustment credits this parent and reduces their support obligation — or increases the other parent's payment.

Key thresholds to know:

• Under 110 overnights: No parenting time adjustment applies
• 110+ overnights: The adjustment kicks in, reducing the obligation of the parent with more overnights
• 182.5 overnights (true 50/50): The higher-earning parent still pays, but the amount is significantly reduced

Moving from 109 to 110 overnights can shift monthly support by several hundred dollars. This is why the parenting time schedule and child support calculation are so tightly linked — and why negotiating the schedule without running the support numbers first can lead to surprises.

Step 5: Determine the Final Order

After calculating each parent's proportionate share, the court subtracts direct expenses already being paid (like health insurance premiums the paying parent already covers) and issues the final monthly support order.

Child support in Arizona cannot be waived by agreement between parents. Even if both parents agree to zero support, the court can reject the agreement if it doesn't adequately provide for the child.

Running the Calculator

Arizona's free calculator is available through the court's ezCourtForms system. You'll need:

• Both parents' gross monthly income
• Number of children
• Each child's age (for the older child adjustment)
• Annual overnight count for each parent
• Monthly health insurance premium for the children
• Monthly work-related childcare costs
• Any agreed-upon education or extraordinary expenses

Run the numbers before you negotiate the parenting schedule. A schedule change from alternating weeks (182 overnights) to a 2-2-5-5 rotation (the overnight count depends on how holidays fall) can shift support by $100-$300/month.

The Arizona Child Custody & Parenting Plan Guide includes a child support worksheet that walks through each calculation step and shows how different parenting schedules affect the final number — so you can compare options before committing to a schedule.

See more Arizona guides →