The stipulation that, if a life insurance policy (or any interest in that policy) is transferred for something of value (money, property, etc.), a portion of the death benefit is subject to be taxed as ordinary income. This portion is equal to the death benefit minus the item(s) of value, as well as any pmiums paid by the transferee at the time of the transfer. For example, if John Doe sells his $250,000 life insurance policy that he has paid $10,000 in pmiums on to Jane Doe for $5,000, the amount subject to income tax is $235,000 ($250,000-$10,000-$5,000).
The transfer-for-value rule includes, but goes beyond, the outright sale of a life insurance policy. The life insurance policy does not lose its tax-exempt status when the policy is transferred to the insured, a partner of the insured or to a company where the insured is an officer or stockholder.