How Child Support Payments are Calculated: A Breakdown of the Process

Raising a child is expensive. A recent study done by Lending Tree found that, on average, it will cost about $300,000 to raise a child through age 18, with costs increasing yearly. Parents are required to provide for their children and must do so after they are no longer together as a couple. When a married couple decides to divorce, they must divide up their marital property in a fair and equitable manner. The court will make an order that also sets child custody and child support. 

Understanding the Purpose of Child Support

Child support is designed to pay for the basic needs of a child. These needs include food, clothes, and housing, along with other minor costs associated with daily living. Both parents are required to contribute to the basic care of their children. Generally, a non-custodial parent must pay child support based on a court order, often as part of the divorce. Since child support is for the essential needs of a child, it does not include extra costs. These may be addressed separately, or they could be included as adjustments to the standardized payment calculation. 

Standardized Payment Calculation

Washington utilizes a standardized calculation system for determining child support payments. This simplifies the determination of support. It is important to note that the judge may use discretion in a child support order, so the actual amount may be lower or higher than the amount you determine using the online calculator. It is helpful to gather necessary data before entering it into an online calculator. Importantly, there are many things that can make these calculations challenging. Before you can estimate payments, you must know the combined monthly net income total for you and your spouse. 

Income That Counts Towards Child Support Calculations

Most types of income count towards the calculation of child support. There are some exceptions to the income calculation. For instance, one-time gifts and prizes are not to be included in income for the purposes of setting child support. Bonuses and other income that is not recurring should not be included in income. It is important to note that the formula requires you to impute a party with income if they are voluntarily underemployed. In other words, a parent cannot voluntarily become unemployed simply to avoid paying their share of child support. 

What Income Does Not Count Towards Child Support Calculations

Some income does not count towards the calculation of child support. These are also called deductions from gross income. While parents must disclose all income, from all sources, some of it may not count when calculating child support obligations. Some of these deductions are the income from a new spouse, child support received for other children, and money from public assistance. Additionally, a parent may deduct income taxes, mandatory pension payments, and union dues, among others. 

Deviations from Standard Child Support

The calculations allow for some deviations when applicable. The judge has the ability to deviate from the standard child support calculations in some cases. It is estimated that about 30% of child support orders deviate from the standard. There are reasons why a child support order may deviate, such as:

• Residential Credit - Child support payments could be reduced if the non-primary parent has substantial residential time with the child. Substantial residential time generally refers to more than 90 overnights with the child in a year. 

• Additional Children - When a non-custodial parent has children from other relationships, the court may adjust the amount of child support downward. The calculations can be complex, so it is helpful to review the details with your attorney. 

There may be other conditions the judge will consider when determining child support payments. Your attorney will review the details of your case and help you estimate child support. 

How are Special Expenses Handled?

As any parent knows, raising a child requires a lot more money than simply providing food and shelter. There are expenses such as daycare costs, school fees, activity costs, fees for athletics, camp costs, and more. In addition, there may be costs for medical or dental care that is not covered by insurance. Generally, extra medical expenses may be provided for on the worksheet in determining support. However, expenses that are covered by the divorce agreement are not included in support calculations. 

Washington Child Support Payment Calculation Tool

Washington utilizes a child support economic table for the calculation of child support. The table is used in conjunction with child support worksheets developed by the Administrative Office of the Courts (AOC). To calculate the amount of child support, you will need to know the combined monthly net income (CMNI). In cases where the CMNI is less than $1,000, the court will review the specific circumstances, but the lowest amount of child support is $50. There is also a maximum presumptive level of child support, which typically applies to a CMNI over $12,000. The child support economic table was revised in 2025 to extend basic support obligation figures up to $50,000 CMNI. A parent’s portion of child support is determined by the proportion of each parent’s income to the total CMNI. 

Washington State provides a quick child support estimator that you can use as a simple guideline. You can find a general estimation of child support by using the Washington State Child Support Schedule Worksheet Calculator. The calculator is designed as a tool only and is for your overall estimation purposes. The worksheet allows you to fill in the details in order to calculate child support payments. These are the worksheets that the court will use when setting child support. The state also utilizes calculations when determining child support in cases where state assistance is necessary. 

Help From a Knowledgeable Attorney

Calculating child support can be complex. This is especially true when a parent is self-employed or owns their own business. You want to make sure that you properly fill out the worksheets so the court can set the correct amount of child support payments. Your attorney may also have access to specialized software that will more efficiently calculate child support, particularly for special circumstances. To learn more, contact our experienced legal team at View Ridge Family Law & Estate Planning at (206) 966-4020 to schedule a consultation.