@rollerskate
You can read the Reg here: https://www.law.cornell.edu/cfr/text/26/1.1014-10
Note that it applies if the decedent's Federal estate tax return is filed after September 17, 2024.
Regardless, you most likely need a value more accurate than merely tacking on 30% to the assessment for property tax purposes by the county assessor and the insured value. The IRS is not obligated to accept anything less than the opinion of fair market value by a licensed real estate appraiser. Failing that, a CMA by a local licensed real estate broker (as of the year 2000 date) would be better than what you currently are using for FMV.
