No. At least not exactly. In general the cost basis of inherited property is the fair market value, on the date of death. You do not need a formal appraisal. The real estate tax appraisal and/or Zillow (and similar sites) is close enough. It doesn't matter when the property is sold. But, yes, you need to determine the FMV on the date of death.
Alternatively, If the administrator of the estate votes to use an alternate valuation date for the estate, the cost basis is then equal to the fair market value of the property or assets either six months following the date of death or the date on which the asset was distributed to the person inheriting it, whichever is earlier.
