State tax filing

The first item on the Income that Illinois handles differently screen is College savings and prepaid tuition plan contributions.  Click Start or Revisit there, and enter your contributions.  See screenshot below.   If you have already went through this section, it will be at the top of the Income that Illinois handles differently page.  

You are allowed to subtract up to $10,000 in contributions if you are single and $20,000 if you are married filing a joint return for contributions you made to the “Bright Start” program, the "College Illinois" Illinois Prepaid Tuition Trust Fund, or the "Bright Directions" program during the tax year. The total subtraction for contributions made to both college savings plans may not exceed $10,000 for single filers and $20,000 for joint filers, even if you contributed more. Contributions to any other IRC Section 529 programs may not be deducted.  See Illinois Dept of Revenue