This Guide will help you change your child support payments by:Answering questions about how and when you can change your child support payments in the "Common Questions" section;Preparing the necessary documents in the "Forms/Letters" section;Explaining the steps to change your child support payments in the "Instructions" section;Giving you more information about child support and filing your court papers for free in the "Related Articles" section; andHelping you find a lawyer, in the "Find Legal Help" section.Click on words that appear like 'this' to learn what these words mean. When can I ask to increase my child support payments? If you are the custodial parent and would like to increase your child support payments, you must:File a Petition to Modify Child Support with the Court; andShow that there has been a substantial change of circumstances since the last child support order was entered.However, if there are special rules for when you can ask for an increase in child support for custodial parents who receive child support enforcement services through the Illinois Department of Healthcare and Family Services. If you would like to talk with a lawyer, click on the "Find Legal Help" tab. When can I ask to lower my child support payments? If you are the non-custodial parent and would like to lower your child support payments, you must:File a Petition to Modify Child Support with the Court; andShow that there has been a substantial change of circumstances since the last child support order was entered. If you want to talk with a lawyer, click on the "Find Legal Help" tab. What does a substantial change in circumstances mean? The court decides if there has been a substantial change in circumstances since the last child support order based on many factors, including: An increase in the non-custodial parent's income from a significant raise or new jobA decrease in the non-custodial parent's income due to a loss of job or disabilityAn increase in the needs of the child requiring child supportThe child has a disability that requires more supportThe child has turned 18The child is no longer living with the custodial parentHow are child support payments calculated? Illinois child support laws require that the parent paying support (non-custodial parent) pay a certain percentage of their net income for child support. The percentage is based on the number of children you are required to support. The judge will use the table below as a guideline for determining the minimum amount for child support payments. The judge may decide to order child support above or below these guidelines depending on the situation. Number of Children Percentage of Supporting Party's Net Income 1 20% 2 28% 3 32% 4 40% 5 45% 6 or more 50%You can calculate net income by adding the total amount of income that the parent gets from all sources and subtracting the following deductions from that total:Federal income tax (properly calculated withholding or estimated payments);State income tax (properly calculated withholding or estimated payments);Social Security (FICA payments);Mandatory retirement contributions required by law or as a condition of employment;Union dues;Dependent and individual health/hospitalization insurance premiums;Prior obligations of support or maintenance actually paid pursuant to a court order;Expenses for repayment of debts that represent reasonable and necessary expenses for the production of income;Medical expenses necessary to preserve life or health; andReasonable expenses for the benefit of the child and the other parent (not gifts).Can child support payments be changed without going to court? No. A Petition to Modify Child Support must be filed with the Court to change child support. The amount of child support owed only changes when the judge enters a new court order that changes it. Until the judge enters a new order, the amount of child support owed will remain the same. If you want your child support to be increased or decreased, it is your responsibility to file a petition asking for child support to be modified. It will not happen automatically. What happens if child support is no longer being paid? If the non-custodial parent stops or decreases child support payments without going to court, the full amount of child support is still owed.Every time a child support payment is due and not paid in full, it gets added to the total debt owed called an arrearage. The child support arrearage accrues interest until it is paid off.