How to Calculate Pro Rata Child Support

The obligation to support a child doesn't end when the relationship ends.

If you're a noncustodial parent, that is, the parent who has physical custody of your child less than half the time, you generally must pay the custodial parent child support. The custodial parent is the parent who has physical custody of your child more than half the time. In many states, the law calculates child support on a pro rata basis.


Step 1

Understand the history. In the past, the amount of child support owed to the custodial parent was strictly based on the noncustodial parent's income. Today, many states, such as Georgia, calculate child support on a pro rata basis. This means many states now consider the noncustodial and custodial parent's income when calculating child support and set the amount in proportion to each parent's income.


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Step 2

Gather your pay stubs. Part of calculating the pro rata amount of child support involves identifying both your and the custodial parent's gross income. Your gross income is the amount of your salary before your employer subtracts money for taxes, insurance, retirement or other deductions from your check. If you and the custodial parent aren't on speaking terms, you may have to make an estimate. Refer to old tax returns or pay stubs if you can.


Step 3

Start subtracting. Certain factors reduce the amount of income the court will consider when determining your child support obligation. For example, if you're already paying child support for two other children, those support obligations will diminish the amount of available income you have for another child. Either parent's status as self-employed could also reduce the amount of income considered.


Step 4

Add your income and the custodial parent's income. Once you have adjusted yours and the custodial parent's income for factors such as child support, add the adjusted income amounts together to determine your total adjusted income amounts. You'll need this amount to navigate your state's Child Support Obligation table.


Step 5

Download your state's Child Support Obligation table. The table tells you the total amount you and the custodial parent owe in child support. Every state is different, so your state may or may not use a table. It also may use a table but refer to it by a different name. If you live in Georgia, it's called a Schedule of Basic Child Support Obligations. The table is made up of columns and rows.


Step 6

Look for the amount of your and the custodial parent's total adjusted income on one of the rows in the table's first column. In the same row that contains your combined adjusted income amounts, you'll see corresponding values that vary based on the number of children involved. The value associated with the number of children involved in your case is the total child support amount both you and the custodial parent are responsible for.


Step 7

Remember your fractions. You will be responsible for only a percentage of the amount identified in the Child Support Obligation table. Determine the percentage by dividing your income by the total adjusted income amount. So for example, if, after adjustments, you earn $40,000 and the custodial parent earns $60,000, your combined adjusted income is $100,000. This means your percentage would be 40 and her percentage would be 60. Accordingly, you would pay 40 percent of the child support while the other parent would pay 60 percent.


Consult a licensed family law attorney in your state for state-specific information on how pro rata child support is calculated.