26 CFR § 20.2056(b)-9 - Denial of double deduction.
The value of an interest in property may not be deducted for Federal estate tax purposes more than once with respect to the same decedent. For example, where a decedent transfers a life estate in a farm to the spouse with a remainder to charity, the entire property is, pursuant to the executor's election under section 2056(b)(7), treated as passing to the spouse. The entire value of the property qualifies for the marital deduction. No part of the value of the property qualifies for a charitable deduction under section 2055 in the decedent's estate.