Divorce: Child Support Law

by Wayne Thomas
The majority of states use the Income Shares Model to calculate child support.

The majority of states use the Income Shares Model to calculate child support.

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Both spouses are obliged to financially support their children after divorce. Courts operate on the assumption that you are directly supporting any child that is living with you. The other parent, typically referred to as the non-custodial parent, is then generally ordered to pay the custodial parent to account for the difference in parenting time. This payment is known as child support and states have different approaches to how it is calculated.

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Income Shares

States differ on their approach to calculating support. The majority of states use what is known as the Incomes Shares Model. This model tries recreate the same proportion of financial support that occurred during marriage. So, if one parent contributed 75 percent of the total household income, he would be responsible for 75 percent of the total amount of the child's support obligation after divorce. The actual dollar amount of payment from the non-custodial parent is contained in the state's child support guidelines and is based on total household income. A few states use a variation of this formula, known as the Melson Formula, which takes additional public policy factors into account, such as a parent's financial needs.

Percentage of Income

An alternative method, used by a smaller number of states, looks only at the non-custodial parent's income. The support obligation is then calculated based on a percentage of that parent's income. Some states use a flat percentage for all income levels while others provide that the percentage decreases as income increases.


After the base support amount is calculated according to a state's formula, certain adjustments are generally allowed. These adjustments include a reduction for the number of overnights the non-custodial parent has with the child and increases for extraordinary expenses, such as private schooling. Some states also allow the non-custodial parent to request a deviation if the obligation is inappropriate or unjust. Deviations are always at the court's discretion.


Once a support obligation is in place, most states allow it to be modified in the future under certain circumstances. Modification usually requires a showing that a change in circumstances has occurred from the date of the original order. Examples of a change in circumstances might include a change in the custody order or significant increase or decrease in the non-custodial parent's income.