Income Shares Model
The most common formula for determining child support is called the income shares model. Under the income shares formula, child support is based on a percentage of the combined income of both parents. For example, if a mother earns $50,000 per year and a father earns $100,000 per year, their combined income is $150,000. The mother's percentage of the shared income is 33 percent and the father's percentage is approximately 67 percent. If your state calculates child support by the percentage of income model, the mother in this example would owe 33 percent of the child's expenses and the father would owe 67 percent.
Percentage of Income Model
Ten states and the District of Columbia utilize the percentage of obligor's income model for calculating child support. Under this theory, the court takes into consideration only the income of the parent paying the child support. This parent is called the obligor. Each state that uses this model requires the obligor to pay child support equal to a certain percentage of his income. Some states require a flat percentage of the income to be paid as child support without consideration of shared parenting time while other states adjust the percentage depending on how much time the obligor spends with his children.
Joint Physical Custody
Physical custody refers to the number of overnights a child spends with each parent. For example, if you see your child every day after school but return her to her mother's house to sleep every night, you do not have any overnight parenting time. The definition of joint physical custody varies by state. Because there are 365 days in a year, a child that spends exactly equal time with each parent would spend 182 overnights in her mother's house and 182 overnights in her father's house each year. However, most states define joint physical custody as any parenting time arrangement where both parents have significant overnights with the child. Significant means more than the common parenting time schedule of every other weekend. For example, some states say that parents share joint physical custody as long as one parent spends at least 123 or 128 overnights with the child per year.
Joint Custody and Income Shares Model
In states that utilize the income shares model for child support, the court uses the number of overnights that the child spends with each parent to calculate the amount of support. The more overnights the obligor has with the child, the lower the support obligation will be because expenses for the child's food, shelter, utilities and clothing increase with the additional time spent with the parent and he will be paying for these expenses directly while the child is in his care.
Joint Custody and Percentage of Income Model
Not all states that utilize the percentage of income model take joint physical custody into consideration when calculating the amount owed for child support. For example, some states simply order child support to be paid as a certain percentage of the parent's income irrespective of the number of overnights. Other states that use this model will take the overnight parenting time into consideration and lower the amount of the child support. For example, if the parent who owes support has 104 overnights with the child, he might be required to pay child support equal to 20 percent of his income, but if he has 180 overnights, he might only be required to pay child support equal to 10 percent of his income.