Income Shares Method of Calculating Support

The income shares model calculates contributions from both parents.

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In 1988, the federal Family Support Act mandated that states select a uniform procedure for calculating child support in all cases that come before a court. The majority of states – 38 as of 2012 – chose the income shares model. It's the more complicated approach, but it's much fairer for the children of divorced parents. It strives to provide the same income and support to kids that they would have had if their parents had remained together.

Basic Computations

The combined incomes of you and your child's other parent form the basis for income shares calculations. The court first determines how much of your combined incomes your child needs to meet basic costs. For example, Florida's statutes dictate that if you and your ex earn $10,000 monthly and if you have one child, $1,437 should be devoted to him. The next step is to determine how much each of you contribute to that $10,000. If you earn $6,000 and your spouse earns $4,000, you're responsible for 60 percent of the $1,437 figure and your ex is responsible for 40 percent. The non-custodial parent makes a cash contribution to the custodial parent – child support – and the custodial parent pays her percentage directly toward the children's needs.

Parenting Time

Not every divorce results in one parent having primary custody and the other having visitation, so many states have incorporated provisions for shared physical custody into their income shares guidelines. The exact method can vary among states, but the non-custodial parent usually receives a deduction from his support obligation commensurate with the amount of additional time his children spend with him, usually over about a third of the year. Some states, such as Massachusetts, calculate child support twice – each calculation assuming that that parent has primary custody. The parent with the higher income then pays the difference between the two calculations to the other parent.

Work-Related Child Care and Health Insurance

States that use the income shares method usually add on the costs of work-related child care to the basic child support obligation. They all address the issue of added expenses for health insurance or medical care as well. However, different states can take different approaches in dealing with these things. For example, both Massachusetts and Florida allow the parent paying health insurance premiums to deduct the cost from his basic child support obligation. Some states cap child care costs at a level that seems reasonable compared to what most providers charge in a given area. For example, if your ex wants to pay her mother $3,000 a month to care for your child while she works, but most providers in your area charge $1,500, the court would most likely enter an order obligating you to pay your percentage share of $1,500, not $3,000.


Child support guidelines are just that – a system of rules and calculations that states must use to compute every child support case. But life is full of extraordinary circumstances, and by law, judges can deviate from income shares calculations to accommodate them. For example, most states' guidelines top out at certain income levels – in Florida, it's $10,000 a month in combined income, and in Massachusetts, it's $250,000 a year. If you and your ex-spouse earn more than this, the court can add to the statutory basic support number in percentage increments based on your income and the number of children you're supporting. States also impute income to parents who are voluntarily under-employed or unemployed. If your ex has her medical license but prefers not to work, the court can assign her income equal to what a doctor in your area typically earns. It doesn't matter if she actually brings in that income – your share of the support obligation would be adjusted accordingly, just as though the money really existed.