Hi Trivedi,

When you prepared the Federal 1040, did you page to the bottom of the "info" screen and do the "non-resident" allocation?  That will let you split the W-2 into the two state amounts and pre-fill the proper columns on the IL CR form.  If your total split between the 2 states does not add up to the W-2 Box 1 total, you will see the error on the non-resident or part year resident allocation sheets.

I know these are available in Professional, but I am not sure they are available in Basic.

Good luck!