Mo. Rev. Stat. § 473.630: Right of retainer.

When a distributee of an estate is indebted to the estate, the amount of the indebtedness if due, or the present worth of the indebtedness, if not due, may be treated as an offset by the executor or administrator against any testate or intestate property, real or personal, of the estate to which such distributee is entitled. An offset hereunder shall be treated as if made as of the time of the death of the decedent and interest shall be adjusted accordingly.