When the actual premium hereafter charged for an insurance by any life insurance company doing business in this state is less than the net premium for such insurance, computed according to the table of mortality and rate of interest prescribed in section 44-403, such company shall be charged as a separate liability with the value of an annuity, the amount of which shall equal the difference between such premium and the term of which, in years, shall equal the number of future annual payments due on such insurance at the date of the valuation. This section shall apply to policies and contracts issued prior to the operative date defined in section 44-407.07.