Iowa uses the Iowa Court Rules Chapter 9 (Child Support Guidelines) to determine child support obligations. Under the Income Shares model, both parents' incomes are combined to estimate what the family would have spent on the child if the household were intact. The obligation is then divided proportionally based on each parent's contribution to combined net income.

Iowa has several distinctive features in its child support system. Iowa uses a distinct "joint physical care" calculation when both parents have 128+ overnights. The joint care formula offsets each parent's obligation — only the difference is paid. Iowa includes a specific adjustment for children's net income (e.g., trust income or Social Security benefits).

Iowa bases calculations on net income — meaning income after mandatory deductions like taxes, Social Security, and Medicare. This gives a more accurate picture of each parent's take-home pay. The self-support reserve in Iowa is $1,230/month, ensuring the paying parent retains enough income to cover basic living expenses.

Iowa recognizes "Joint Physical Care" when the non-custodial parent has the children for at least 128 overnights per year (approximately 35% of the time). When this threshold is met, the standard child support formula is adjusted to reflect the increased direct expenses borne by both parents.

Under Iowa's Income Shares approach, the shared parenting adjustment typically calculates each parent's obligation based on their income share, then applies a credit or cross-calculation that accounts for the time each parent directly supports the child. The more overnights the non-custodial parent has, the greater the reduction in their payment — but the adjustment is not dollar-for-dollar because fixed costs like housing don't decrease when the child is away.

Below 128 overnights, Iowa generally treats the arrangement as a sole custody situation with standard visitation, and no custody time adjustment is applied to the child support calculation.