@wsaslow wrote:
My mother passed away in November 2021. Her apartment in Florida was left to my sister and I (50%/50%) after probate which completed in April of 2022. We sold it within a month or so.
First of all, you do not need to file anything in Florida since Florida does not levy an individual income tax (nor an estate or inheritance tax).
Also, I agree with @DavidD66 that your basis for the condo is the fair market value on the date of death of your mother, but disagree that it is a reasonable assumption that there was no increase in value between the date of death (November of 2021) and the date of the sale (April-May of 2022).
I happen to live in Florida and can tell you that many areas saw a dramatic spike in real estate prices during the first quarter of 2022. I have no idea whether your condo was impacted but you would need to be able to substantiate whatever dollar figure you use as your basis should it ever be questioned by the IRS.
Although a formal appraisal by a certified real estate appraiser is the only evidence of value the IRS is required to accept, you can probably get away with a competitive market analysis (CMA) from a local real estate agent.
