In Illinois, if a spouse or ex-spouse owes past due child support or other child related support obligations established by court order, the Illinois Department of Revenue can withhold tax refund payments for the spouse owing support obligations, and pay those refunds to the oblige spouse. 305 ILCS 5/10-17.5.

The Illinois Department of Revenue cannot initiate collection activities for child support arrearages (and other child related support obligations). The Illinois Department of Healthcare and Family Services is responsible for certifying past-due child support amounts to the Comptroller of the state of Illinois and to the Illinois Department of Revenue. The purpose of the certification process is to ensure that all past due child support obligations are accurate and final, and provides notice and opportunity for the obligor spouse to contest the arrearage amount.

Once certified, the Illinois Department of Revenue may collect the child support delinquency using authorized methods for tax collection. 305 ILCS 5/10-17.5, -5/10-17.9 and 86 Ill. Adm. Code 100.9020.

Under the Internal Revenue Code, 26 United States Code 6402 and -6305, the IRS can withhold tax refunds from an ex-spouse, and from an obligor in a parentage proceeding, an pay the withheld money to the ex-spouse oblige, and oblige a parenting proceeding, to pay down the arrearage. The Internal Revenue Code calls this ''child and spouse support" and "offset of past due support against overpayments." As is the case with the state of Illinois, there must be a certification of the amount due.

With the IRS, the certification is obtained from the Department of Health and Human Services (DHS). The obligor is given notice of the pending certification and is allowed to challenge the amount claimed. With the IRS, the child support must have been paid through the State Disbursement Unit (SDU). If the child support was not paid through the SDU, the child support arrearage can still be placed with the SDU to allow certification to proceed.