No. Line 3 is not a negative number (324). Line 3 is sum of Line 1, the value found on IL-1040 Line 14 which is the value of the tax due based on the Net Income (324), minus Line 2 which is the value of any Tax Credits that were paid (0). The form correctly does this (Line 1 or 324 minus Line 2 or 0 equals 324) and inserts 324 into Line 3. Line 4g is calculated based on the Property Tax paid which is 5% of Line 4a which is also a positive number (657). Line 5 should compare Lines 3 (324) and Line 4g (657) and insert the value of the lowest (324). It does not. Instead, it inserts a 0 in Line 5. I have tried overriding the values in Lines 1, 3, and 4g with other values. In all cases the value for Line 5 is always 0. I also notice the same issue with Line 8 of the same form.
