Per IRS Publication 525 Taxable and Nontaxable Income, page 21:
Life Insurance Proceeds
Life insurance proceeds paid to you because of the death of the insured person aren't taxable unless the policy was turned over to you for a price. This is true even if the proceeds were paid under an accident or health insurance policy or an endowment contract. However, interest income received as a result of life insurance proceeds may be taxable.
Proceeds not received in installments. If death benefits are paid to you in a lump sum or other than at regular intervals, include in your income only the benefits that are more than the amount payable to you at the time of the insured person's death. If the benefit payable at death isn't specified, you include in your income the benefit payments that are more than the present value of the payments at the time of death.
Proceeds received in installments. If you receive life insurance proceeds in installments, you can exclude part of each installment from your income.
To determine the excluded part, divide the amount held by the insurance company (generally, the total lump sum payable at the death of the insured person) by the number of installments to be paid. Include anything over this excluded part in your income as interest.
Example. The face amount of the policy is $75,000 and, as beneficiary, you choose to receive 120 monthly installments of $1,000 each. The excluded part of each installment is $625 ($75,000 รท 120), or $7,500 for an entire year. The rest of each payment, $375 a month (or $4,500 for an entire year), is interest income to you.
Installments for life. If, as the beneficiary under an insurance contract, you're entitled to receive the proceeds in installments for the rest of your life without a refund or period-certain guarantee, you figure the excluded part of each installment by dividing the amount held by the insurance company by your life expectancy. If there is a refund or period-certain guarantee, the amount held by the insurance company for this purpose is reduced by the actuarial value of the guarantee.