Code of Federal Regulations Title 26. Internal Revenue § 26.20.2040–1 Joint interests

(1) To the extent that the property was acquired by the decedent and the other joint owner or owners by gift, devise, bequest, or inheritance, the decedent's fractional share of the property is included.

(2) In all other cases, the entire value of the property is included except such part of the entire value as is attributable to the amount of the consideration in money or money's worth furnished by the other joint owner or owners. See § 20.2043–1 with respect to adequacy of consideration. Such part of the entire value is that portion of the entire value of the property at the decedent's death or at the alternate valuation date described in section 2032 which the consideration in money or money's worth furnished by the other joint owner or owners bears to the total cost of acquisition and capital additions. In determining the consideration furnished by the other joint owner or owners, there is taken into account only that portion of such consideration which is shown not to be attributable to money or other property acquired by the other joint owner or owners from the decedent for less than a full and adequate consideration in money or money's worth.

(1) If the decedent furnished the entire purchase price of the jointly held property, the value of the entire property is included in his gross estate;

(2) If the decedent furnished a part only of the purchase price, only a corresponding portion of the value of the property is so included;

(3) If the decedent furnished no part of the purchase price, no part of the value of the property is so included;

(4) If the decedent, before the acquisition of the property by himself and the other joint owner, gave the latter a sum of money or other property which thereafter became the other joint owner's entire contribution to the purchase price, then the value of the entire property is so included, notwithstanding the fact that the other property may have appreciated in value due to market conditions between the time of the gift and the time of the acquisition of the jointly held property;

(5) If the decedent, before the acquisition of the property by himself and the other joint owner, transferred to the latter for less than an adequate and full consideration in money or money's worth other income-producing property, the income from which belonged to and became the other joint owner's entire contribution to the purchase price, then the value of the jointly held property less that portion attributable to the income which the other joint owner did furnish is included in the decedent's gross estate;

(6) If the property originally belonged to the other joint owner and the decedent purchased his interest from the other joint owner, only that portion of the value of the property attributable to the consideration paid by the decedent is included;

(7) If the decedent and his spouse acquired the property by will or gift as tenants by the entirety, one-half of the value of the property is included in the decedent's gross estate;  and

(8) If the decedent and his two brothers acquired the property by will or gift as joint tenants, one-third of the value of the property is so included.