Turbotax (Premium) asked me for the original price paid (for what was my primary residence when I bought it in 1997). I started renting it out in 2018 and sold it in 2021. Without any other data, I used 80%-20% for the home-land value. Turbotax used the 80% (purchase price) to derive 'cost or other basis' in line 21 of form 4797. (I'm not sure exactly how they calculated it; it's about 20% lower than the home purchase price.)
Unless I missed something, Turbotax never asked about costs of capital improvements (made between 1997 and 2018). Do just add my costs of capital improvements (new kitchen, roof, windows, siding...) to the number Turbotax put in line 21?
