In the interview, SweetieJean references, TurboTax will ask for the "Expenses of Sale" That's where you enter the deductible closing costs. In actuality they are not "deducted" but added to your cost basis to reduce your capital gain. Review IRS Pub 523, page 11, for a list of the expenses you can consider as sales expenses. <a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/p523.pdf">https://www.irs.gov/pub/irs-pdf/p523.pdf</a>
As others have indicated, mortgage payoff is not a closing cost and is not deducted or added to your cost basis. It is simply not taken into account at all.
