Subject to the limitation prescribed in subsection (c), the credit provided by this section shall be an amount which bears the same ratio to the estate tax paid (adjusted as indicated hereinafter) with respect to the estate of the transferor as the value of the property transferred bears to the taxable estate of the transferor (determined for purposes of the estate tax) decreased by any death taxes paid with respect to such estate. For purposes of the preceding sentence, the estate tax paid shall be the Federal estate tax paid increased by any credits allowed against such estate tax under section 2012, or corresponding provisions of prior laws, on account of gift tax, and for any credits allowed against such estate tax under this section on account of prior transfers where the transferor acquired property from a person who died within 10 years before the death of the decedent.
If the credit provided in this section relates to property received from 2 or more transferors, the limitation provided in paragraph (1) of this subsection shall be computed by aggregating the value of the property so transferred to the decedent. The aggregate limitation so determined shall be apportioned in accordance with the value of the property transferred to the decedent by each transferor.
For purposes of this section, the term “property” includes any beneficial interest in property, including a general power of appointment (as defined in section 2041).