Mo. Rev. Stat. § 145.041: Estate containing property having tax situs outside Missouri — computation of tax.

If the decedent's estate contains property having a tax situs not within the state of Missouri, then the tax determined by section 145.011 shall be reduced to an amount determined by multiplying the tax by a fraction whose numerator is the gross estate excluding all property having a tax situs not within the state of Missouri at the decedent's death and whose denominator is the gross estate. In determining the fraction, no deductions shall be considered and the gross estate shall not be reduced by a mortgage or other indebtedness for which the decedent's estate is not liable.