Form 712 is a statement of valuation to be used in filing a Form 706 Federal Estate Filing or equivalent state-level estate or inheritance tax filing if the Estate is liable because of total valuation of the Estate or by local state law.
It is not an Income Tax filing or information. Generally the death benefit proceeds of a life insurance policy do not represent income and are not subject to income tax.
However, it is not unusual for the proceeds to be held by the life insurance company during a period of processing the claim for the death benefits, such that interest income is generated for that delay time period. If so, a Form 1099-INT would be issued reporting the interest income only.