Most states in the U.S. use a standard calculator to determine child support that is based off of collective income and set guidelines for what it costs to raise a child in that state. Here’s how it works:

Step 1: Tallying income to determine child support

State guidelines take into consideration the income of both parents when determining child support. Some states use gross income in their calculations, others use net income. Each parent’s income is tallied, and then added together to get a combined total. Here are some things you should know about how income is determined:

1. Parents are required to swear to the accuracy of these statements, and documentation will be required in the form of pay stubs, employer statements, income tax returns, or in the case of small business owners, profit and loss statements.
2. Any type of alimony or spousal support is added to the income of the spouse who receives it, and deducted from the income of the spouse who pays it.
3. There also may be additional deductions/allowances that are used to adjust this income. (See child support income deductions, outlined in the next section.)
4. If a person has seasonal employment or a fluctuating income, then this may be averaged over several years of recent work history to determine their income.
5. In some cases, “imputed income” may be applied in child support determinations. This essentially means that if one person is not working, is in school, or has failed to produce documentation of income, then an income will be assigned to them based on things like that parent’s earning potential within their particular occupation or their most recent work history.
6. Income attributable to subsequent spouses or other persons who may reside with the parent is not considered as part of that person’s income.
7. Income from overtime or taking on a second job cannot be used to adjust child support. It is assumed that income from these endeavors is used to better one’s current situation, and does not count towards determining child support awards. (It may, however, be garnished to collect back child support already owed.)

Step 2: Calculating child support

Child support is then determined according to the state’s formula, which takes each parent’s income and divides it by the total to get a percentage amount of total income. That percentage is then calculated according to set guidelines for what the state has determined to be the typical annual cost of raising a child that age. For example, if a mother is earning $40,000/year and the father $60,000, then the mother would be obligated to cover 40% of the financial costs for that child, the dad 60%. If the state has determined that $10,000 in child support each year is appropriate, then the mother’s financial obligation would be $4,000, the dad’s $6,000.

From there things get a little more nuanced, depending on the situation. In joint-custody situations, it may be common practice to take the difference between each parent’s obligations and award it accordingly. For example, in the situation described above, the difference between dad’s $6,000 obligation and mom’s $4,000 obligation is $2,000, resulting in a child support payment from dad to mom of just under $200 a month. Even though raising the child together, dad has more resources than mom, so this is meant to even the resources. If mom has sole custody or even primary custody with dad on a visitation schedule, then standard practice might be to have dad pay his share ($6,000) to the primary parent, resulting in a child support payment of $500 a month. Or if dad has custody and mom is on a visitation schedule, she might pay $4,000 (or just over $380 a month) to dad.

Since each state does things their own way, it’s hard for us to tell you precisely what to expect. But this should give you a general idea of the criteria and methods that are used to determine child support.