Investment yield
(a) Investment yield defined. Section 804(c) defines the term investment yield of a life insurance company for purposes of part I, subchapter L, chapter 1 of the Code. Investment yield means gross investment income (as defined in section 804(b) and paragraph (a) of 1.804-3), less the deductions provided in section 804(c) and paragraph (b) of this section for investment expenses, real estate expenses, depreciation, depletion, and trade or business (other than an insurance business) expenses. However, such expenses are deductible only to the extent that they relate to investment income and the deduction of such expenses is not disallowed by any other provision of subtitle A of the Code. For example, investment expenses are not allowable unless they are ordinary and necessary expenses within the meaning of section 162, and under section 265, no deduction is allowable for interest on indebtedness incurred or continued to purchase or carry obligations the interest on which is wholly exempt from taxation under chapter 1 of the Code. A deduction shall not be permitted with respect to the same item more than once.
Source
26 CFR § 1.804-4
Scoping language
for purposes of part I, subchapter L, chapter 1