I foolishly agreed yesterday to prepare the 2021 returns for a panicked client who forgot I retired and, of course, in addition to the normal 1 W2, he bought a house in July 2020 to flip and sold it in February 2021.

I haven't had a client with this situation previously and after researching Pub 544, I believe this is investment income with a short term capital gain result. Taxpayer did not live in or try to rent the house. Form 1099S was not issued.

Am I correct to report it as an investment on Schedule D? Thank you.