"House was vacant until sold."

Okay, trying to combine Both Topics:

The house is inherited for FMV on the date of death. You state it was "maintenance and repairs to keep it" but it seems that was prep to sell it, since no one was living in it. And, if it was listed at a reasonable price and the same listing finally got it sold, that sale sort of proves FMV. The assessor office is never a FMV listing; it's a Tax Value listing.

Either get an appraisal for the date of the death, or I would ride on the fact that it sold as timely as possible for a FMV that applied, given there are not unusual changes in conditions for the property (such as, someone realized a shopping center was going next door or found gold on the property or something) and there is no loss from FMV. Just usual closing costs, as Lisa pointed out.