It's IT-2664.
For federal tax purposes, there are certain closing costs (but not all) that are considered adjustments to cost basis when determining capital gains tax. The allowable and non-allowable closing costs are listed here starting on page 8.
https://www.irs.gov/pub/irs-pdf/p523.pdf
Form IT-2664 says to use the same federal rules for this form.
On worksheet 2. you are asked to enter the purchase price and adjustments to basis including "closing costs" (line 7). This refers to closing costs for the purchase. On line 15 you are asked to enter the selling price less expenses. This refers only to those expenses of selling that are allowable adjustments to closing costs. So the short answer is that closing costs on line 7 refers to the purchase, and selling expenses on line 15 refers to the sale, but only those costs that are allowable adjustments to basis.
What @Critter-3 is referring to is the fact that if you report a sales price of $550,000 (net after adjustments) but the IRS gets paperwork saying the unadjusted sales price was $600,000, they may send you a letter asking for an explanation, not because you did anything wrong, but because of how the IRS computers work. She is suggesting that you report the unadjusted selling price on line 15, and include your closing costs from the sale on line 7 along with the closing costs from the purchase. I haven't had this problem so I can't recommend one method over another. Form IT-2664 puts the closing costs from the purchase and from the sale in two different places.
One thing you must not do is double-count your closing costs. Don't include closing costs from the sale on line 7 if you are also reporting the adjusted selling price on line 15, since that would be double-counting your closing costs.
