Missouri Revised Statutes '474.160
Election by surviving spouse to take against will, effect
1. When a married person dies testate as to any part of his estate, a right of election is given to the surviving spouse solely under the limitations and conditions herein stated:
(1) The surviving spouse, upon election to take against the will, shall receive in addition to exempt property[1] and the allowance under section 474.260[2] one-half of the estate, subject to the payment of claims, if there are no lineal descendants of the testator; or, if there are lineal descendants of the testator, the surviving spouse shall receive one-third of the estate subject to the payment of claims;
(2) When a surviving spouse elects to take against the will he shall be deemed to take by descent, as a modified share, such part of the estate as comes to him under the provisions of this section, and shall take nothing under the will;
(3) Whenever there is an effective election to take against a will which provides for benefits to accrue upon the death of the surviving spouse, the election has the same effect as to the benefits as if the surviving spouse had predeceased the testator, unless the will otherwise provides.
2. The rights of the surviving spouse under this section are not given in lieu of the homestead allowance under section 474.290[3], but any homestead allowance made to the surviving spouse shall be offset against the share taken under this section.
Missouri Revised Statutes '474.163.
Valuation of estate, how determined
1. For the purposes of section 474.160, the estate consists of all money and property owned by the decedent at his death, reduced by funeral and administration expenses, exempt property, family allowance and enforceable claims, and increased by the aggregate value of all money and property derived by the surviving spouse from the decedent by any means other than testate or intestate succession, exempt property or family allowance without a full consideration in money or money's worth. The aggregate value of money and property so derived by the surviving spouse from the decedent shall be offset against the elective share given by section 474.160.
2. Property derived from the decedent includes, but is not limited to:
(1) Any beneficial interest of the surviving spouse in a trust created by the decedent during his lifetime;
(2) Any property appointed to the spouse by the decedent's exercise of a general or special power of appointment also exercisable in favor of persons other than the spouse;
(3) Any proceeds of insurance, including accidental death benefits, on the life of the decedent attributable to premiums paid by him;
(4) Any lump sum immediately payable, and the commuted value of the proceeds of annuity contracts under which the decedent was the primary annuitant, attributable to premiums paid by him;
(5) The commuted value of amounts payable after the decedent's death under any public or private pension, disability compensation, death benefit or retirement plan, exclusive of the Federal Social Security system, by reason of service performed or disabilities incurred by the decedent; and
(6) The value of the share of the surviving spouse resulting from rights in community property in any other state formerly owned with the decedent. * * *
3. When immediately before the decedent's death the surviving spouse was a cotenant or remainderman with respect to money, property, a trust fund or an account in a bank or other financial institution and, incident to such death, the surviving spouse became the sole owner thereof or the owner of a life interest therein, the whole value of such sole ownership or life interest shall be deemed to have been received from the decedent, except as to the proportion of such value, if any, derived from contributions toward the acquisition, establishment or creation of the money, property, fund or account made by the surviving spouse or ascendant or collateral blood relatives of the surviving spouse, other than the decedent. * * *
5. Property owned by the surviving spouse as of the decedent's death, or previously transferred by the surviving spouse, is presumed to have been derived from the decedent, except to the extent that the surviving spouse establishes that it was derived from another source.
6. If it appears that the elective share given by section 474.160, as computed in accordance with this section, will be less advantageous to the surviving spouse than the provision made for that spouse by the will, the surviving spouse may rescind the election to take against the will.
7. Nothing in this section shall be deemed to require the surviving spouse to refund to the estate money or property derived from the decedent or its value.
[1]Exempt property: AThe surviving spouse, or unmarried minor children of a decedent are entitled absolutely to the following property of the estate without regard to its value: The family bible and other books, one automobile or other passenger motor vehicle, including a pickup truck, with its means of propulsion, all wearing apparel of the family, all household electrical appliances, all household musical and other amusement instruments and all household and kitchen furniture, appliances, utensils and implements. Such property shall belong to the surviving spouse, if any, otherwise to the unmarried minor children in equal shares.@
[2]This section allows the court to grant to the surviving spouse, and to any children whom the decedent had a obligation to support, a living allowance from the decedent=s estate for a period of up to one year. The statute does not fix the amount of the allowance, but allows the court to determine the amount after considering Athe previous standard of living of the applicant, the condition of the estate, the income and other assets available to the applicant and the applicant's expenses.@
[3]The homestead allowance may be granted by the court at the petition of the surviving spouse or unmarried minor children. It cannot exceed $15,000 or one-half of the estate, whichever is greater. It is exempt from all claims against the estate.