The IWO is the OMBapproved form (PDF) used for income withholding in tribal, intrastate, and interstate cases as well as all child support orders. Instructs employers and federal agencies on how to process income withholding orders including examples of calculations.This form is used to notify an employer to withhold wages from a noncustodial parent when they have past-due child support. View the form in English. If you have any changes to report, please complete the second page of the form to the child support enforcement agency (CSEA) named above. Complete Form W-4 so that your employer can withhold the correct federal income tax from your pay. Give Form W-4 to your employer. What do I do with the IWO form? And when a parent doesn't voluntarily meet their child support obligations, employers might be involved in the child support process. Other items you may find useful.