Example (1). H (the decedent) devised real property to W (his surviving wife) for life, with remainder to A and his heirs. The interest which passed from H to W is a nondeductible interest since it will terminate upon her death and A (or his heirs or assigns) will thereafter possess or enjoy the property.
Example (2). H bequeathed the residue of his estate in trust for the benefit of W and A. The trust income is to be paid to W for life, and upon her death the corpus is to be distributed to A or his issue. However, if A should die without issue, leaving W surviving, the corpus is then to be distributed to W. The interest which passed from H to W is a nondeductible interest since it will terminate in the event of her death if A or his issue survive, and A or his issue will thereafter possess or enjoy the property.
Example (3). H during his lifetime purchased an annuity contract providing for payments to himself for life and then to W for life if she should survive him. Upon the death of the survivor of H and W, the excess, if any, of the cost of the contract over the annuity payments theretofore made was to be refunded to A. The interest which passed from H to W is a nondeductible interest since A may possess or enjoy a part of the property following the termination of the interest of W. If, however, the contract provided for no refund upon the death of the survivor of H and W, or provided that any refund was to go to the estate of the survivor, then the interest which passed from H to W is (to the extent it is included in H's gross estate) a deductible interest.
Example (4). H, in contemplation of death, transferred a residence to A for life with remainder to W provided W survives A, but if W predeceases A, the property is to pass to B and his heirs. If it is assumed that H died during A's lifetime, and the value of the residence was included in determining the value of his gross estate, the interest which passed from H to W is a nondeductible interest since it will terminate if W predeceases A and the property will thereafter be possessed or enjoyed by B (or his heirs or assigns). This result is not affected by B's assignment of his interest during H's lifetime, whether made in favor of W or another person, since the term "assigns" (as used in section 2056(b)(1)(B)) includes such an assignee. However, if it is assumed that A predeceased H, the interest of B in the property was extinguished, and, viewed as of the time of the subsequent death of H, the interest which passed from him to W is the entire interest in the property and, therefore, a deductible interest.
Example (5). H transferred real property to A by gift (reserving the right to the rentals of the property for a term of 20 years. H died within the 20-year term, bequeathing the right to the remaining rentals to a trust for the benefit of W. The terms of the trust satisfy the five conditions stated in § 20.2056(b)-5 , so that the property interest which passed in trust is considered to have passed from H to W. However, the interest is a nondeductible interest since it will terminate upon the expiration of the term and A will thereafter possess or enjoy the property.
Example (6). H bequeathed a patent to W and A as tenants in common. In this case, the interest of W will terminate upon the expiration of the term of the patent, but possession or enjoyment of the property by A must necessarily cease at the same time. Therefore, since A's possession or enjoyment cannot outlast the termination of W's interest, the latter is a deductible interest.
Example (7). A decedent bequeathed $100,000 to his wife, subject to a direction to his executor to use the bequest for the purchase of an annuity for the wife. The bequest is a nondeductible interest.
Example (8). Assume that pursuant to local law an allowance for support is payable to the decedent's surviving spouse during the period of the administration of the decedent's estate, but that upon her death or remarriage during such period her right to any further allowance will terminate. Assume further that the surviving spouse is sole beneficiary of the decedent's estate. Under such circumstances, the allowance constitutes a deductible interest since any part of the allowance not receivable by the surviving spouse during her lifetime will pass to her estate under the terms of the decedent's will. If, in this example, the decedent bequeathed only one-third of his residuary estate to his surviving spouse, then two-thirds of the allowance for support would constitute a nondeductible terminable interest.
26 C.F.R. §20.2056(b)-1