Per IL Schedule ICR Instructions, pages 3 & 4:

Am I eligible for a property tax credit?

You may figure a credit for the Illinois property taxes you paid in 2012 on your principal residence (not a vacation home or rental property) for the time you owned and lived at the property during 2011, if that residence was in Illinois. Nonresidents of Illinois may not take this credit.

You may not figure a credit for mobile home privilege tax, penalties, or fees included in your property tax bill, or the portion of the property that is deductible as a business expense.

Section A: Illinois Property Tax Credit

Line 4a - Write the total amount of Illinois Property Tax paid during the tax year for the real estate that includes your principal residence.

Line 4b - Write the property number, sometimes called "parcel number" or "permanent number" for the property listed on Line 4a.

Note: If you and your spouse each have a principal residence and have included the property tax paid on both residences in Line 4a, enter the property number for the second residence on Line 4c.

Lines 4c and 4d - Write the property numbers for any adjoining lots to your principal residence, if used for residential purposes, for which you are claiming a property tax credit.

Note: Your property number is found near the top of your property tax bill or assessment notice. If your property taxes are paid through your mortgage, you may contact your lender for your property number.

You may also get this number from your county assessor's office. A list of counties, with contact information, is under the "Individuals" section of the Illinois website.