child support calculation

Effective July 1, 2017 Public Act 99-0764 will substantially change how child support is calculated. Illinois has adopted an income shares model for child support which will eliminate the current one-size-fits-all method of simply taking a percentage of the noncustodial parent’s net income.


The new method of calculating child support is more fair and equitable. The new child support calculation considers both parents’ incomes in determining child support rather than just basing support on the non-custodial parent. The current percentage calculation of child support is simplistic and fails to consider the actual costs of the children, parenting time or the income of the custodial parent.


As of July 1st, child support will be calculated by determining the combined net income (after taxes) of both parents. The percentage share of income for each parent is then determined relative to the total combined net income. The next step includes looking at a chart of Basic Child Support Obligation and locating the corresponding figure based on the parents’ combined monthly net income and number of children. This number represents the basic child support obligation for both parents. The Basic Support Obligation chart will be maintained and updated by the Department of Healthcare and Family Services and has yet to be released as of the date of this article. The chart relies on economic studies of actual child rearing costs based on the income levels of both parents.

The basic child support obligation for each parent is then determined by taking their share of the combined income multiplied by the figure found in the Basic Child Support Obligation chart. That number represents each parent's individual share of the basic support obligation. It should be noted that a figure is calculated for each parent, but the obligation for the parent with most of the parenting time is assumed to spend their share of the child support obligation on the child and will retain their share of the basic support obligation.

The basic child support obligation can be found by finding the income shares table based on the combined adjusted net income at The child support estimator can be found at


The statute provides for two separate formulas to determine the net income of the parties. The parties can use the standardized tax amount or the individualized tax amount. The standardized tax amount is a simplified formula and includes both parents claiming a single taxpayer status and includes standardized deductions for federal and state taxes, Social Security and Medicare taxes. A more accurate method to calculate the net income is to use the individualized tax amount formula which is based on the actual tax deductions used by both parties.


Maintenance payments from one parent to another shall be subtracted from the payor’s gross income and shall be included in the receiving parent’s gross income. As such, maintenance is subtracted and/or added prior to deducting taxes.


Another adjustment to income is court ordered child support. The adjustment for separate child support obligations is made after taxes are deducted from the gross income. It is permissible to receive an adjustment for support paid to another person even if there is no court order requiring the payment of child support.


An adjustment is allowed for shared parenting when both parents have 146 parenting overnights or more per year. The formula for shared parenting includes multiplying the basic support obligation as determined by the Basic Support Obligation table by 1.5 and then cross-multiplied by the percentage share of parenting time to the other parent. This number is then set-off by subtracting the lesser support obligation from the greater number.


It should be noted that the following child related expenses are not included in the basic child support obligation and may be added based on the parent’s percentage share of combined net income:

  • Daycare
  • Extracurricular expenses
  • School registration fees
  • Health care insurance premiums
  • Out of pocket medical expenses

If you are seeking child support or have an existing child support obligation, it is imperative that you consult with an attorney at The Law Office of J. Patrick Nelson, PC. As you can see, the new child support statute drastically changes the way child support will be calculated as of July 1st. Please contact The Law Office of J. Patrick Nelson, PC and schedule a consultation to discuss your case. There is no fee for an initial consultation; and we can answer any questions you may have. The attorneys at The Law Office of J. Patrick Nelson, PC provide a high level of professionalism and experience in handling divorce and family law matters.

Categories: Child Support, Divorce