Illinois doesn't give a refund for property taxes - it gives a credit of 5% (of the property taxes paid) off your Illinois taxes due. If you did not live in, or have earnings from, Illinois in 2018, you would have no Illinois taxes due, thus no basis for the property tax credit and no need to file an Illinois tax return.
If you itemize, you can deduct your portion of the 2018 property tax on your federal return.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
