Rejection code IL1040-10000-1 - From the state of Illinois: "The Secondary Taxpayer Prior Year Adjusted Gross Income (AGI) did not match the Prior Year AGI on the Illinois Department of Revenue (IDOR) production file.
When you get to the screen that asks you if you filed a tax return in 2023, click the box that says "I don't have my AGI from those tax years." It will take you to a screen that will ask for either your IL PIN or your driver's license. You can find your IL PIN by going to this website: https://mytax.illinois.gov/_/#1
One common cause of the IL1040-8100-1 reject code is inaccurate personal information, such as misspelled names or incorrect Social Security numbers.
Revisit your Personal Info (or My Info) page and recheck that your information is correct.