What do you do if you no longer have a 1979 tax return with Form 2119 (deferred cap gains for house sale)?
I am doing my mother's taxes who became a widow late 2021. She sold the house she lived in since 1979 with my father last year (2022), so I need to figure out if she owes any taxes. When they bought that house in 1979, they had sold their previous house also in 1979 at some gain, and I am assuming that gain was deferred via form 2119 on their 1979 taxes. However, that 1979 tax return no longer exists for me to determine the amount of the gain from the previous house that was rolled into the new house. I have rough estimates of what they paid for the previous house and what they sold it for. And with the step up in basis on half the house value due to my father's passing, and the $500K joint exemption my mother is still entitled to since she sold within 2 years of my father's death, I am quite sure she is not going to have to pay anything even if my estimates for the 1979 Form 2119 are off by as much as $10-20K (although I am pretty sure I would not be off more than few thousand dollars at most). So what do I do, as I of course do not want to get audited, as I have nothing to back up what I do other than educated guestimates?
