At this point, i would suggest either deleting your Illinois NR return and start over, or review the entries in the other income section. it sounds like there is some income reported elsewhere that Illinois is trying to tax. If you have another state in your return, you will need to allocate income between the two states.
As you prepare your Illinois non-resident return, it will ask you what portion of the income was earned in Illinois. Keep in mind, as you are preparing the Illinois return, it will ask about EACH income item you already reported in your federal return. Just make sure you only record the amount of income earned in Illinois for each income item it asks for.
If you still have problems, please reach out to customer phone support as they have the ability to view your return to pinpoint the issues that you may be experiencing.
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Thanks! I actually found this reviewing my return in PDF form which means I had already paid, and paying precludes you from starting over. The fix in the end (after getting absolutely nowhere with customer phone support) was deleting all my state forms in the tools section and starting that return over. Still no explanation as to how this amount ended up in the IL form.