Complete the worksheet on the back of this page to figure the correct number of allowances you are entitled to claim. Give your completed Form IL-W-4 to your.Complete Form W-4 so that your employer can withhold the correct federal income tax from your pay. Complete a new Form W4P, Withholding Certificate for Pension or Annuity Payments, and submit it to your payer. Use the following pages to complete your Illinois State and Federal income tax withholding, or W-4 information. Individuals who earned U.S.-based income must file additional documentation.