at original purchase, break  out land$$ vs buildings/other assets. It's an "land" entry in column to right of asset entry, dates, $$ amounts, etc. ( you can go back even today and do that--but it will screw up all depreciation probably, unless you didn't add land to the building ). When recording sale on this tax return, go to asset/building and record sale--it asks if you want to record separately. I usually do an EXCEL sheet of original purchase to get %, multiply against sale $$.